Films comprising bright silver based quaternary nanostructures

ABSTRACT

Disclosed are films comprising Ag, In, Ga, and S (AIGS) nanostructures and at least one ligand bound to the nanostructures. In some embodiment, the AIGS nanostructures have a photon conversion efficiency of greater than 32% and a peak wavelength emission of 480-545 nm. In some embodiments, the nanostructures have an emission spectrum with a FWHM of 24-38 nm.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to the field of nanotechnology. More particularly,the invention provides thin, heavy metal-free nanostructure colorconversion films that have high photon conversion efficiency (PCE) ofgreater than 32% at a peak emission wavelength of 480-545 nm, whenexcited using a blue light source with a wavelength about 450 nm.

Background Art

Efficient conversion of color is important for lighting and displayapplications. In display applications, a blue light source with awavelength around 450 nm is most commonly used as a backlight. Mostapplications require materials free from heavy metals such as Cd and Pb.

Increased efficiency leads to less wasted power as well as increasedemission. Color conversion thin films are characterized by photonconversion efficiency (PCE), which is defined as the number of emittedphotons divided by the number of source photons. Green heavy metal freeQD color conversion films used for displays typically have poorperformance due to their limited absorption in blue light where they areexcited. Blue absorption is often inherently limited by the materialsystem being used, which results in a much thicker film being requiredto absorb sufficient 450 nm light.

The thin films formed by deposition of QD inks are typically cured by UVirradiation. In many cases, this is followed by thermal processing at180° C. for up to 1 hour in the presence of air. Photon conversionefficiency of these films is limited by a combination of poor absorptionand poor light conversion due to instability through these processingsteps.

A need remains in the art for Ag/In/Ga/S (AIGS) nanostructures with highband edge emission (BE), narrow full width at half maximum (FWHM), highquantum yield (QY), and reduced red-shifting, and which are useful inpreparing films that have high (greater than 32%) photon conversionefficiency (PCE) at a peak emission wavelength between 480 and 545 nm,using an excitation wavelength of about 450 nm.

BRIEF SUMMARY OF THE INVENTION

The invention provides thin, heavy metal-free nanostructure colorconversion films that have high photon conversion efficiency (PCE) ofgreater than 32% at a peak emission wavelength of 480-545 nm, whenexcited using a blue light source with a wavelength about 450 nm. Thisis accomplished by using Ag/In/Ga/S (AIGS) nanostructures in an inkformulation containing one or more ligands, with all handling of theinks, followed by deposition, processing and measurement of films beingdone in an oxygen-free environment prior to being exposed to blue orultraviolet light. In some embodiments, the AIGS nanostructures have aFWHM of 28-38 nm. In other embodiments, the AIGS nanostructures have aFWHM of less than 32 nm. This narrow FWHM is accomplished by adding atleast one polyamino-ligand to AIGS nanostructures and making a filmlayer, with all handling of the nanostructure inks, deposition of theinks, processing and measurement of the films being done in anoxygen-free environment.

Thin films formed by deposition of QD inks are typically cured by UVirradiation. In many cases, this is followed by thermal processing at180° C. for up to 1 hour in the presence of air. It has been discoveredthat photon conversion efficiency is reduced by poor absorption and poorlight conversion due to instability through these processing steps.

Disclosed herein are films comprising AIGS nanostructures, in an inkformulation comprising at least one ligand, that achieve PCEs of greaterthan (>) 32% after thermal processing. In some embodiments, provided isa film comprising AIGS nanostructures, at least one ligand, and exhibita PCE of greater than 32% at a peak emission wavelength of 480-545 nm,when excited using a blue light source with a wavelength of 450 nm. ThePCE is calculated by integrating the emission spectrum from 484 nm to700 nm, with the green portion being defined as 484-588 nm. In someembodiments, the films are thin (5-15 μm) color-conversion films.

These films, as prepared, have good (>95%) blue light absorption atabout 450 nm but moderate emission properties. However, when processedin the absence of oxygen and/or light and/or encapsulated beforeexposing the films to UV or blue light, the emissive properties of thesefilms are improved significantly.

In some embodiments, the film further comprises at least one monomerincorporated into the ligands coating the AIGS surface. In someembodiments, the at least one monomer is an acrylate. In someembodiments, the monomer is at least one of ethyl acrylate,hexamethylene diacrylate (HDDA), tetrahydrofurfuryl acrylate,tri(propylene glycol) diacrylate, 1,4-bis(acryloyloxy)butane orisobornyl acrylate.

Provided is a method of preparing the AIGS film, comprising:

(a) providing AIGS nanostructures and at least one ligand coating thenanostructures;

(b) admixing at least one organic resin with AIGS nanostructures of (a);and

(c) preparing a first film comprising the admixed AIGS nanostructures,the at least one ligand coating the nanostructures, and the at least oneorganic resin on a first barrier layer;

(d) curing the film by UV irradiation and/or baking;

(e) encapsulating the first film between the first barrier layer and asecond barrier layer; and

wherein the encapsulated film exhibits a conversion efficiency (PCE) ofgreater than 32% at a peak emission wavelength of 480-545 nm, whenexcited using a blue light source with a wavelength of about 450 nm.

In some embodiments, the AIGS nanostructures further comprise at leastone monomer incorporated into the at least one ligand coating the AIGSsurface.

Also provided is a method further comprising:

(f) addition of at least one oxygen reactive material in the mixture ofAIGS nanostructures and ligand of (a), addition of at least one oxygenreactive material in the admixture of (b), and/or forming a second filmcomprising at least one oxygen reactive material on top of the firstfilm prepared in (c); and/or

(g) forming a sacrificial barrier layer on the first film prepared in(c) that temporarily blocks oxygen and/or water, and measuring the PCEof the film, then removing the sacrificial barrier layer.

Also provided is a method comprising:

(a) encapsulating the films before thermal processing and/ormeasurement;

(b) use of oxygen reactive materials as part of the formulation duringthermal processing or light exposure; and/or

(c) temporary blocking of oxygen through the use of a sacrificialbarrier layer.

In some embodiments, the nanostructures have an emission spectrum with aFWHM of less than 40 nm. In some embodiments, the nanostructures have anemission spectrum with a FWHM of 24-38 nm. In some embodiments, thenanostructures have an emission spectrum with a FWHM of 27-32 nm. Insome embodiments, the nanostructures have an emission spectrum with aFWHM of 29-31 nm.

In some embodiments, the nanostructures have a QY of 80-99.9%. In someembodiments, the nanostructures have a QY of 85-95%. In someembodiments, the nanostructures have a QY of about 86-94%. In someembodiments, the nanostructures have an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹)greater than or equal to 0.8, where OD is optical density. In someembodiments, the nanostructures have an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) in theinclusive range 0.8-2.5. In some embodiments, the nanostructures have anOD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) in the inclusive range 0.87-1.9. In someembodiments, the average diameter of the nanostructures is less than 10nm by transmission electron microscopy (TEM). In some embodiments, theaverage diameter is about 5 nm.

In some embodiments, at least about 80% of the emission is band-edgeemission. In some embodiments, at least about 90% of the emission isband-edge emission. In some embodiments, 92-98% of the emission isband-edge emission. In some embodiments, 93-96% of the emission isband-edge emission.

In some embodiments, the AIGS nanostructures have a peak emissionwavelength (PWL) of about 450 nm.

In some embodiments, the at least one ligand is an amino ligand,polyamino ligand, a ligand comprising a mercapto group, or a ligandcomprising a silane group. It was discovered unexpectedly that the useof a polyamino ligand leads to AIGS containing films with a FWHM ofgreater than 32 nm.

In some embodiments, the at least one polyamino-ligand is a polyaminoalkane, a polyamino-cycloalkane, a polyamino heterocyclic compound, apolyamino functionalized silicone, or a polyamino substituted ethyleneglycol. In some embodiments, the polyamino-ligand is a C₂₋₂₀alkane orC₂₋₂₀ cycloalkane substituted by two or three amino groups andoptionally containing one or two amino groups in place of a carbongroup. In some embodiments, the polyamino-ligand is1,3-cyclohexanebis(methylamine), 2,2-dimethyl-1,3-propanediamine, ortris(2-aminoethyl)amine.

In some embodiments, the ligand is a compound of formula I:

wherein:

x is 1 to 100;

y is 0 to 100; and

R² is C₁₋₂₀ alkyl.

In some embodiments, x=19, y=3, and R²=—CH₃.

In some embodiments, the at least one ligand is(3-aminopropyl)trimethoxy-silane); (3-mercaptopropyl)triethoxysilane;DL-α-lipoic acid; 3,6-dioxa-1,8-octanedithiol; 6-mercapto-1-hexanol;methoxypolyethylene glycol amine (about m.w. 500); poly(ethyleneglycol)methyl ether thiol (about m.w. 800); diethyl phenylphosphonite; dibenzylN,N-diisopropylphosphoramidite; di-tert-butylN,N-diisopropylphosphoramidite; tris(2-carboxyethyl)phosphinehydrochloride; poly(ethylene glycol) methyl ether thiol (about m.w.2000); methoxypolyethylene glycol amine (about m.w. 750); acrylamide; orpolyethylenimine. M.w. of the polymers is determined by massspectrometry.

In some embodiments, the at least one ligand is a combination ofamino-polyalkylene oxide (about m.w. 1000) and methoxypolyethyleneglycol amine (about m.w. 500); amino-polyalkylene oxide (about m.w.1000) and 6-mercapto-1-hexanol; amino-polyalkylene oxide (about m.w.1000) and (3-mercaptopropyl)triethoxysilane; and 6-mercapto-1-hexanoland methoxypolyethylene glycol amine (about m.w. 500).

In some embodiments, the AIGS nanostructures further comprise at leastone monomer incorporated into the at least one ligand coating the AIGSsurface.

Also provided is a nanostructure composition comprising:

(a) AIGS nanostructures exhibiting a PCE of greater than 32%, and

(b) at least one organic resin.

In some embodiments, the at least one organic resin is cured.

Also provided is a method of preparing the nanostructure compositionsdescribed herein, the method comprising:

(a) providing AIGS nanostructures and at least one ligand coating thenanostructures;

(b) admixing at least one organic resin with the nanostructures of (a);

(c) preparing a first film comprising the admixed AIGS nanostructures,the at least one ligand coating the nanostructures, and the at least oneorganic resin on a first barrier layer;

(d) curing the film by UV irradiation and/or baking; and

(e) encapsulating the first film between the first barrier layer and asecond barrier layer,

wherein the encapsulated film exhibits a conversion efficiency (PCE) ofgreater than 32% at a peak emission wavelength of 480-545 nm, whenexcited using a blue light source with a wavelength of about 450 nm.

In some embodiments, the nanostructures of (a) further comprise at leastone monomer incorporated into the ligands coating the AIGS surface. Insome embodiments, the at least one monomer is an acrylate. In someembodiments, the monomer is at least one of ethyl acrylate, HDDA,tetrahydrofurfuryl acrylate, tri(propylene glycol) diacrylate,1,4-bis(acryloyloxy)butane or isobornyl acrylate.

In some embodiments, the method is carried out before the encapsulatedfilm is exposed in air to measurement of the emission spectra of theAIGS nanostructures. In some embodiments, the method is carried outunder an inert atmosphere.

In some embodiments, the method further comprises:

(f) addition of at least one oxygen reactive material in the mixture ofAIGS nanostructures and ligand of (a),

(g) addition of at least one oxygen reactive material in the admixtureof (b), and/or

(h) forming a second film comprising at least one oxygen reactivematerial on top of the first film prepared in (c); and/or

(i) forming a sacrificial barrier layer on the first film prepared in(c) that temporarily blocks oxygen and/or water, and measuring the PCEof the film, then removing the sacrificial barrier layer.

In some embodiments, the two barrier layers exclude oxygen and/or water.

In some embodiments, 92-98% of the emission is band-edge emission. Insome embodiments, 93-96% of the emission is band-edge emission.

Also provided is a method of preparing a composition, comprising

(a) providing a comprising AIGS nanostructures and at least one ligandcoating the nanostructure surface; and

(b) admixing the composition obtained in (a) with at least one secondligand.

In some embodiments, the composition in (a) further comprises an organicresin. In some embodiments, the composition in (a) further comprises atleast one monomer incorporated into the ligands coating the AIGSsurface. In some embodiments, the method further comprises ink-jetprinting the composition.

In some embodiments, the method further comprises preparing a filmcomprising the composition obtained in (b). In some embodiments, themethod further comprises curing the film. In some embodiments, the filmis cured by heating. In some embodiments, the film is cured by exposingto electromagnetic radiation.

Also provided is a device comprising the films described above.

Also provided is a nanostructure molded article comprising:

(a) a first conductive layer;

(b) a second conductive layer; and

(c) a film comprising an AIGS nanostructure layer between the firstconductive layer and the second conductive layer,

wherein the nanostructure layer comprises AIGS nanostructures having aPCE of greater than 32%.

Also provided is a nanostructure color converter comprising

a back plane;

a display panel disposed on the back plane; and

a film comprising an AIGS nanostructure layer comprising AIGSnanostructures having a PCE of greater than 32%, the nanostructure layerdisposed on the display panel.

In some embodiments, the nanostructure layer comprises a patternednanostructure layer. In some embodiments, the back plane comprises anLED, an LCD, an OLED, or a microLED.

Further features and advantages of the invention, as well as thestructure and operation of various embodiments of the invention, aredescribed in detail below with reference to the accompanying drawings.It is noted that the invention is not limited to the specificembodiments described herein. Such embodiments are presented herein forillustrative purposes only. Additional embodiments will be apparent topersons skilled in the relevant art(s) based on the teachings containedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate the present embodiments and, togetherwith the description, further serve to explain the principles of thepresent embodiments and to enable a person skilled in the relevantart(s) to make and use the present embodiments.

FIG. 1 is a photograph of, from left to right, first and third filmsthat did not contain a polyamino ligand and which exhibited extensionwrinkling. The second and fourth films containing the polyamino ligandshowed no wrinkling.

FIGS. 2A-2C and TEM images showing AIGS nanostructures before ionexchange treatment (FIG. 2A), after a single ion exchange treatment(FIG. 2B) and after two ion exchange treatments (FIG. 2C).

FIGS. 3A and 3B are schematics for unencapsulated (FIG. 3A) andencapsulated (FIG. 3B) films.

FIG. 4 is a scatter graph showing the QY % exhibited by mixtures ofvarious ligands.

FIG. 5 is a scatter graph showing ligand combinations that provideimproved QY % (good combination) and combinations that provide reducedQY % (bad combination).

FIG. 6 is a graph showing QY % of various ligand combinations beforeligand exchange (NG), after ligand exchange (LE), and after a thermaltest for 30 min.

FIG. 8 is a graph showing QY % of various ligand combinations at variousligand ratios.

FIG. 9 is two scatter graphs showing the PCE of AIGS films baked at 180°C., without (left graph) and with encapsulation before PCE measurement(right graph).

FIG. 10 is a bar graph showing the photoluminescence quantum yield(PLQY) of AIGS nanostructures that were ligand exchanged in varioussolvents at room temperature and 80° C.

FIG. 11 is a bar graph showing the QY of ligand exchanged AIGSnanostructures in the presence of various monomers.

FIG. 12 is a line graph showing the film external quantum efficiency(EQE) of AIGS nanostructures that were ligand exchanged and treated withvarious monomers and after UV curing.

FIG. 13 is a bar graph showing the blue light absorption of AIGSnanostructure inks that were ligand exchanged, treated with variousmonomers, and spun coated at 800 rpm.

FIG. 14 is a line graph showing the effect of diamine((1,3-bis(aminomethyl)cyclohexane) on film EQE after UV and post bake at180° C. for 30 min (POB).

FIG. 15 is a line graph showing the effect of added diamine onviscosity, measured indirectly as blue light absorption in films afterspin coating at 800 RPM.

FIG. 16 is a bar graph showing the effect of ligand exchange (LE) with adiamine (DA) on solution QY. The graph shows that the QY drop afterheating at 180° C. became smaller with increasing amounts of diamine.

FIG. 17 is a line graph showing the effect of increasing amounts of DAon film PCE after UV curing.

FIG. 18 is a line graph showing the effect on film blue light absorbanceby increasing amounts of DA in a film.

FIG. 19 is a line graph showing the effect on PCE film blue lightabsorbance of added DA in the monomer dispersion, in the LE, and in boththe monomer dispersion and LE.

FIG. 20 is a line graph showing the effect on film viscosity and bluelight absorbance of added DA in the monomer dispersion, in the LE, andin both the monomer dispersion and LE.

FIG. 21 is a line graph showing the effects of various additives oninitial film EQE.

FIG. 22 is a line graph showing the effect of various additives on filmEQE after POB.

FIG. 23 is a line graph showing the effect of film EQE and blue lightabsorption with additional additives.

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements. The drawing in which an elementfirst appears is indicated by the leftmost digit(s) in the correspondingreference number. Unless otherwise indicated, the drawings providedthroughout the disclosure should not be interpreted as to-scaledrawings.

DETAILED DESCRIPTION OF THE INVENTION Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention pertains. The following definitionssupplement those in the art and are directed to the current applicationand are not to be imputed to any related or unrelated case, e.g., to anycommonly owned patent or application. Although any methods and materialssimilar or equivalent to those described herein can be used in thepractice for testing of the present invention, the preferred materialsand methods are described herein. Accordingly, the terminology usedherein is for the purpose of describing particular embodiments only, andis not intended to be limiting.

As used in this specification and the appended claims, the singularforms “a,” “an” and “the” include plural referents unless the contextclearly dictates otherwise. Thus, for example, reference to “ananostructure” includes a plurality of such nanostructures, and thelike.

The term “about” as used herein indicates the value of a given quantityvaries by +/−10% of the value. For example, “about 100 nm” encompasses arange of sizes from 90 nm to 110 nm, inclusive.

A “nanostructure” is a structure having at least one region orcharacteristic dimension with a dimension of less than about 500 nm. Insome embodiments, the nanostructure has a dimension of less than about200 nm, less than about 100 nm, less than about 50 nm, less than about20 nm, or less than about 10 nm. Typically, the region or characteristicdimension will be along the smallest axis of the structure. Examples ofsuch structures include nanowires, nanorods, nanotubes, branchednanostructures, nanotetrapods, tripods, bipods, nanocrystals, nanodots,quantum dots, nanoparticles, and the like. Nanostructures can be, e.g.,substantially crystalline, substantially monocrystalline,polycrystalline, amorphous, or a combination thereof. In someembodiments, each of the three dimensions of the nanostructure has adimension of less than about 500 nm, less than about 200 nm, less thanabout 100 nm, less than about 50 nm, less than about 20 nm, or less thanabout 10 nm.

The term “heterostructure” when used with reference to nanostructuresrefers to nanostructures characterized by at least two different and/ordistinguishable material types. Typically, one region of thenanostructure comprises a first material type, while a second region ofthe nanostructure comprises a second material type. In certainembodiments, the nanostructure comprises a core of a first material andat least one shell of a second (or third etc.) material, where thedifferent material types are distributed radially about the long axis ofa nanowire, a long axis of an arm of a branched nanowire, or the centerof a nanocrystal, for example. A shell can but need not completely coverthe adjacent materials to be considered a shell or for the nanostructureto be considered a heterostructure; for example, a nanocrystalcharacterized by a core of one material covered with small islands of asecond material is a heterostructure. In other embodiments, thedifferent material types are distributed at different locations withinthe nanostructure; e.g., along the major (long) axis of a nanowire oralong a long axis of arm of a branched nanowire. Different regionswithin a heterostructure can comprise entirely different materials, orthe different regions can comprise a base material (e.g., silicon)having different dopants or different concentrations of the same dopant.

As used herein, the “diameter” of a nanostructure refers to the diameterof a cross-section normal to a first axis of the nanostructure, wherethe first axis has the greatest difference in length with respect to thesecond and third axes (the second and third axes are the two axes whoselengths most nearly equal each other). The first axis is not necessarilythe longest axis of the nanostructure; e.g., for a disk-shapednanostructure, the cross-section would be a substantially circularcross-section normal to the short longitudinal axis of the disk. Wherethe cross-section is not circular, the diameter is the average of themajor and minor axes of that cross-section. For an elongated or highaspect ratio nanostructure, such as a nanowire, the diameter is measuredacross a cross-section perpendicular to the longest axis of thenanowire. For a spherical nanostructure, the diameter is measured fromone side to the other through the center of the sphere.

The terms “crystalline” or “substantially crystalline,” when used withrespect to nanostructures, refer to the fact that the nanostructurestypically exhibit long-range ordering across one or more dimensions ofthe structure. It will be understood by one of skill in the art that theterm “long range ordering” will depend on the absolute size of thespecific nanostructures, as ordering for a single crystal cannot extendbeyond the boundaries of the crystal. In this case, “long-rangeordering” will mean substantial order across at least the majority ofthe dimension of the nanostructure. In some instances, a nanostructurecan bear an oxide or other coating, or can be comprised of a core and atleast one shell. In such instances it will be appreciated that theoxide, shell(s), or other coating can but need not exhibit such ordering(e.g. it can be amorphous, polycrystalline, or otherwise). In suchinstances, the phrase “crystalline,” “substantially crystalline,”“substantially monocrystalline,” or “monocrystalline” refers to thecentral core of the nanostructure (excluding the coating layers orshells). The terms “crystalline” or “substantially crystalline” as usedherein are intended to also encompass structures comprising variousdefects, stacking faults, atomic substitutions, and the like, as long asthe structure exhibits substantial long range ordering (e.g., order overat least about 80% of the length of at least one axis of thenanostructure or its core). In addition, it will be appreciated that theinterface between a core and the outside of a nanostructure or between acore and an adjacent shell or between a shell and a second adjacentshell may contain non-crystalline regions and may even be amorphous.This does not prevent the nanostructure from being crystalline orsubstantially crystalline as defined herein.

The term “monocrystalline” when used with respect to a nanostructureindicates that the nanostructure is substantially crystalline andcomprises substantially a single crystal. When used with respect to ananostructure heterostructure comprising a core and one or more shells,“monocrystalline” indicates that the core is substantially crystallineand comprises substantially a single crystal.

A “nanocrystal” is a nanostructure that is substantiallymonocrystalline. A nanocrystal thus has at least one region orcharacteristic dimension with a dimension of less than about 500 nm. Insome embodiments, the nanocrystal has a dimension of less than about 200nm, less than about 100 nm, less than about 50 nm, less than about 20nm, or less than about 10 nm. The term “nanocrystal” is intended toencompass substantially monocrystalline nanostructures comprisingvarious defects, stacking faults, atomic substitutions, and the like, aswell as substantially monocrystalline nanostructures without suchdefects, faults, or substitutions. In the case of nanocrystalheterostructures comprising a core and one or more shells, the core ofthe nanocrystal is typically substantially monocrystalline, but theshell(s) need not be. In some embodiments, each of the three dimensionsof the nanocrystal has a dimension of less than about 500 nm, less thanabout 200 nm, less than about 100 nm, less than about 50 nm, less thanabout 20 nm, or less than about 10 nm.

The term “quantum dot” (or “dot”) refers to a nanocrystal that exhibitsquantum confinement or exciton confinement. Quantum dots can besubstantially homogeneous in material properties, or in certainembodiments, can be heterogeneous, e.g., including a core and at leastone shell. The optical properties of quantum dots can be influenced bytheir particle size, chemical composition, and/or surface composition,and can be determined by suitable optical testing available in the art.The ability to tailor the nanocrystal size, e.g., in the range betweenabout 1 nm and about 15 nm, enables photoemission coverage in the entireoptical spectrum to offer great versatility in color rendering.

The term “oxygen-free ligand” refers to coordinating molecules that donot contain oxygen atoms that are able to coordinate to, or react with,metal ions used herein.

A “ligand” is a molecule capable of interacting (whether weakly orstrongly) with one or more faces of a nanostructure, e.g., throughcovalent, ionic, van der Waals, or other molecular interactions with thesurface of the nanostructure.

“Photoluminescence quantum yield” (QY) is the ratio of photons emittedto photons absorbed, e.g., by a nanostructure or population ofnanostructures. As known in the art, quantum yield is typicallydetermined by the absolute change in photon counts upon illumination ofthe sample inside an integrating sphere, or a comparative method usingwell-characterized standard samples with known quantum yield values.

“Peak emission wavelength” (PWL) is the wavelength where the radiometricemission spectrum of the light source reaches its maximum.

As used herein, the term “full width at half-maximum” (FWHM) is ameasure of the size distribution of nanostructures. The emission spectraof nanostructures generally have the shape of a Gaussian curve. Thewidth of the Gaussian curve is defined as the FWHM and gives an idea ofthe size distribution of the particles. A smaller FWHM corresponds to anarrower nanostructure nanocrystal size distribution. FWHM is alsodependent upon the emission wavelength maximum.

Band-edge emission is centered at higher energies (lower wavelengths)with a smaller offset from the absorption onset energy as compared tothe corresponding defect emission. Additionally, the band-edge emissionhas a narrower distribution of wavelengths compared to the defectemission. Both band-edge and defect emission follow normal(approximately Gaussian) wavelength distributions.

Optical density (OD) is a commonly used method to quantify theconcentration of solutes or nanoparticles. As per Beer-Lambert's law,the absorbance (also known as “extinction”) of a particular sample isproportional to the concentration of solutes that absorb a particularwavelength of light.

Optical density is the optical attenuation per centimeter of material asmeasured using a standard spectrometer, typically specified with a 1 cmpath length. Nanostructure solutions are often measured by their opticaldensity in place of mass or molar concentration because it is directlyproportional to concentration and it is a more convenient way to expressthe amount of optical absorption taking place in the nanostructuresolution at the wavelength of interest. A nanostructure solution thathas an OD of 100 is 100 times more concentrated (has 100 times moreparticles per mL) than a product that has an OD of 1.

Optical density can be measured at any wavelength of interest, such asat the wavelength chosen to excite a fluorescent nanostructure. Opticaldensity is a measure of the intensity that is lost when light passesthrough a nanostructure solution at a particular wavelength and iscalculated using the formula:

OD=log₁₀*(I _(OUT) /I _(IN))

where:

I_(OUT)=the intensity of radiation passing into the cell; and

I_(IN)=the intensity of radiation transmitted through the cell.

The optical density of a nanostructure solution can be measured using aUV-VIS spectrometer. Thus, through the use of a UV-VIS spectrometer itis possible to calculate the optical density to determine the amount ofnanostructures that are present in a sample.

Unless clearly indicated otherwise, ranges listed herein are inclusive.

A variety of additional terms are defined or otherwise characterizedherein.

AIGS Nanostructures

Provided are nanostructures comprising Ag, In, Ga, and S, wherein thenanostructures have a peak emission wavelength (PWL) between 480-545 nm.In some embodiments, at least about 80% of the emission is band-edgeemission. The percentage of band-edge emission is calculated by fittingthe Gaussian peaks (typically 2 or more) of the nanostructures emissionspectrum and comparing the area of the peak that is closer in energy tothe nanostructure bandgap (which represents the band-edge emission) tothe sum of all peak areas (band-edge+defect emission).

In one embodiment, the nanostructures have a FWHM emission spectrum ofless than 40 nm. In another embodiment, the nanostructures have a FWHMof 36-38 nm. In some embodiments, the nanostructure have an emissionspectrum with a FWHM of 27-32 nm. In some embodiments, the nanostructurehave an emission spectrum with a FWHM of 29-31 nm.

In another embodiment, the nanostructures have a QY of about 80% to99.9%. In another embodiment, the nanostructures have a QY of 85-95%. Inanother embodiment, the nanostructures have a QY of about 86% to about94%. In some embodiments, at least 80% of the emission is band-edgeemission. In other embodiments, at least 90% of the emission isband-edge emission. In other embodiments, at least 95% of the emissionis band-edge emission. In some embodiments, 92-98% of the emission isband-edge emission. In some embodiments, 93-96% of the emission isband-edge emission.

The AIGS nanostructures provide high blue light absorption. As apredictive value for blue light absorption efficiency, the opticaldensity at 450 nm on a per mass basis (OD₄₅₀/mass) is calculated bymeasuring the optical density of a nanostructure solution in a 1 cm pathlength cuvette and dividing by the dry mass per mL (mg/mL) of the samesolution after removing all volatiles under vacuum (<200 mTorr). In oneembodiment, the nanostructures provided herein have an OD₄₅₀/mass(mL·mg⁻¹·cm⁻¹) of at least 0.8. In another embodiment, thenanostructures have an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) of 0.8-2.5. In anotherembodiment, the nanostructures have an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) of0.87-1.9.

In one embodiment, the nanostructures have been treated with galliumions such that ion exchange of gallium for indium occurs throughout theAIGS nanostructure. In another embodiment, the nanostructures have Ag,In, Ga, and S in the core and treated by ion exchange with gallium ionsand S. In another embodiment, the nanostructures have Ag, In, Ga, and Sin the core and treated by ion exchange with silver ions, gallium ionsand S. In some embodiments, the ion exchange treatment leads to agradient of gallium, silver and/or sulfur throughout the nanostructures.

In one embodiment, the average diameter of the nanostructures is lessthan 10 nm as measured by TEM. In another embodiment, the averagediameter is about 5 nm. AIGS Nanostructures Prepared Using a GaX₃ (X=F,Cl, or Br) Precursor and an Oxygen-Free Ligand

Reports of AIGS preparation in the literature have not attempted toexclude oxygen-containing ligands. In the coating of AIGS with gallium,oxygen-containing ligands are often used to stabilize the Ga precursor.Commonly gallium(III) acetylacetonate is used as an easily air-handledprecursor, whereas Ga(III) chloride requires careful handling due tomoisture sensitivity. For example, in Kameyama et al., ACS Appl. Mater.Interfaces 10:42844-42855 (2018), gallium (III) acetylacetonate was usedas the precursor for core and core/shell structures. Since gallium has ahigh affinity for oxygen, oxygen-containing ligands and using a galliumprecursor that was not prepared under oxygen-free conditions may produceunwanted side reactions, such as gallium oxides, when Ga and Sprecursors are used to produce nanostructures that contain a significantgallium content. These side reactions may lead to defects in thenanostructures and result in lower quantum yields.

In some embodiments, AIGS nanostructures are prepared using oxygen-freeGaX₃ (X=F, Cl, or Br) as a precursor in the preparation of the AIGScore. In some embodiments, AIGS nanostructures are prepared using GaX₃(X=F, Cl, or Br) as a precursor and an oxygen-free ligand in thepreparation of Ga enriched AIGS nanostructures. In some embodiments,AIGS nanostructures are prepared using GaX₃ (X=F, Cl, or Br) as aprecursor and an oxygen-free ligand in the preparation of the AIGS core.In some embodiments, AIGS nanostructures are prepared using GaX₃ (X=F,Cl, or Br) as a precursor and an oxygen-free ligand in the preparationof the AIGS core and in the ion exchange treatment the AIGS cores.

Provided are nanostructures comprising Ag, In, Ga, and S, wherein thenanostructures have a peak emission wavelength (PWL) between 480-545 nm,and wherein the nanostructures were prepared using a GaX₃ (X=F, Cl, orBr) precursor and an oxygen-free ligand.

In some embodiments, the nanostructures prepared using a GaX₃ (X=F, Cl,or Br) precursor and an oxygen-free ligand display a FWHM emissionspectrum of 35 nm or less. In some embodiments, the nanostructuresprepared using a GaX₃ (X=F, Cl, or Br) precursor and an oxygen-freeligand display a FWHM of 30-38 nm. In some embodiments, thenanostructures prepared using a GaX₃ (X=F, Cl, or Br) precursor and anoxygen-free ligand have a QY of at least 75%. In some embodiments, thenanostructures prepared using a GaX₃ (X=F, Cl, or Br) precursor and anoxygen-free ligand have a QY of 75-90%. In some embodiments, thenanostructures prepared using GaX₃ (X=F, Cl, or Br) precursor and anoxygen-free ligand have a QY of about 80%.

The AIGS nanostructures prepared herein provide high blue lightabsorption. In some embodiments, the nanostructures have an OD₄₅₀/mass(mL·mg⁻¹·cm⁻¹) of at least 0.8. In some embodiments, the nanostructureshave an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) of 0.8-2.5. In another embodiment, thenanostructures have an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) of 0.87-1.9.

In some embodiments, the nanostructures are treated with gallium ionssuch that ion exchange of gallium for indium occurs throughout the AIGSnanostructure. In some embodiments, the nanostructures comprise Ag, In,Ga, and S in the core with a gradient of gallium between the surface andthe center of the nanostructure. In some embodiments, the nanostructuresare AIGS cores treated with AGS and are prepared using a GaX₃ (X=F, Cl,or Br) precursor and an oxygen-free ligand in the core. In someembodiments, the nanostructures are AIGS nanostructures are preparedusing a GaX₃ (X=F, Cl, or Br) precursor and an oxygen-free ligand. Insome embodiments, the AIGS nanostructures are prepared by reacting apre-formed In—Ga reagent with Ag₂S nanostructures to give AIGSnanostructures, followed by ion exchange with gallium by reacting withan oxygen-free Ga salt to form the AIGS nanostructures.

Methods of Making AIGS Nanostructures

Provided are methods of making the AIGS nanostructures, comprising:

(a) preparing a mixture comprising AIGS cores, a sulfur source, and aligand;

(b) adding the mixture obtained in (a) to a mixture of a galliumcarboxylate and a ligand at a temperature of 180-300° C. to giveion-exchanged nanostructures with a gradient of gallium from the surfaceto the center of the nanostructures; and

(c) isolating the nanostructures.

In some embodiments, the nanostructures have a PWL of 480-545 nm,wherein at least about 60% of the emission is band-edge emission.

Also provided is method of making the AIGS nanostructures, comprising

(a) reacting Ga(acetylacetonate)₃, InCl₃, and a ligand optionally in asolvent at a temperature sufficient to give an In—Ga reagent, and

(b) reacting the In—Ga reagent with Ag₂S nanostructures at a temperaturesufficient to make AIGS nanostructures,

(c) reacting the AIGS nanostructures with an oxygen-free Ga salt in asolvent containing a ligand at a temperature sufficient to giveion-exchanged nanostructures with a gradient of gallium from the surfaceto the center of the nanostructures.

In some embodiments, the nanostructures have a PWL of 480-545 nm,wherein at least about 60% of the emission is band-edge emission.

In some embodiments, the ligand is an alkyl amine. In some embodiments,the alkylamine ligand is oleylamine. In some embodiment, the ligand isused in excess and acts as a solvent and the recited solvent is absentin the reaction. In some embodiments, the solvent is present in thereaction. In some embodiment, the solvent is a high boiling solvent. Insome embodiments, the solvent is octadecene, squalane, dibenzyl ether orxylene. In some embodiments, the temperature sufficient in (a) is 100 to280° C.; the temperature sufficient in (b) is 150 to 260° C.; and thetemperature sufficient in (c) is 170 to 280° C. In some embodiments, thetemperature sufficient in (a) is about 210° C., the temperaturesufficient in (b) is about 210° C., and the temperature sufficient in(c) is about 240° C.

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 90% of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission. In some embodiments, 92-98% of the emission isband-edge emission. In some embodiments, 93-96% of the emission isband-edge emission.

Examples of ligands are disclosed in U.S. Pat. Nos. 7,572,395,8,143,703, 8,425,803, 8,563,133, 8,916,064, 9,005,480, 9,139,770, and9,169,435, and in U.S. Patent Application Publication No. 2008/0118755.In one embodiment, the ligand is an alkyl amine. In some embodiments,the ligand is an alkyl amine selected from the group consisting ofdodecylamine, oleylamine, hexadecylamine, dioctylamine, andoctadecylamine.

In some embodiments, the sulfur source in (a) comprisestrioctylphosphine sulfide, elemental sulfur, octanethiol, dodecanethiol,octadecanethiol, tributylphosphine sulfide, cyclohexyl isothiocyanate,α-toluenethiol, ethylene trithiocarbonate, allyl mercaptan,bis(trimethylsilyl) sulfide, trioctylphosphine sulfide, or combinationsthereof. In some embodiments, the sulfur source in (a) is derived fromS₈.

In one embodiment, the sulfur source is derived from S₈.

In one embodiment, the temperature in (a) and (b) is about 270° C.

In some embodiments, the mixture in (b) further comprises a solvent. Insome embodiments, the solvent is trioctylphosphine, dibenzyl ether, orsqualane.

In some embodiments, the gallium carboxylate is a gallium C₂₋₂₄carboxylate. Examples of C₂₋₂₄ carboxylates include acetate, propionate,butanoate, pentanoate, hexanoate, heptanoate, octanoate, nonanoate,decanoate, undecanoate, tridecanoate, tetradecanoate, pentadecanoate,hexadecanoate, octadecanoate (oleate), nonadecanoate, and icosanoate. Inone embodiment, the gallium carboxylate is gallium oleate.

In some embodiments, the ratio of gallium carboxylate to AIGS cores is0.008-0.2 mmol gallium carboxylate per mg AIGS. In one embodiment, theratio of gallium carboxylate to AIGS cores is about 0.04 mmol galliumcarboxylate per mg AIGS.

In a further embodiment, the AIGS nanostructures are isolated, e.g., byprecipitation. In some embodiments, the AIGS nanostructures areprecipitated by addition of a non-solvent for the AIGS nanostructures.In some embodiments, the non-solvent is a toluene/ethanol mixture. Theprecipitated nanostructures may be further isolated by centrifugationand washing with a non-solvent for the nanostructures.

Also provided is a method of making the nanostructures, comprising:

(a) preparing a mixture comprising AIGS cores and a gallium halide in asolvent and holding the mixture for a time sufficient to giveion-exchanged nanostructures with a gradient of gallium from the surfaceto the center of the nanostructures; and

(b) isolating the nanostructures.

In some embodiments, the nanostructures have a PWL of 480-545 nm, andwherein at least about 60% of the emission is band-edge emission.

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 90% of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission.

In some embodiments, the gallium halide is gallium chloride, bromide oriodide. In one embodiment, the gallium halide is gallium iodide.

In some embodiments, the solvent comprises trioctylphosphine. In someembodiments, the solvent comprises toluene.

In some embodiments, the time sufficient in (a) is from 0.1-200 hours.In some embodiments, the time sufficient in (a) is about 20 hours.

In some embodiments, the mixture is held at 20 to 100° C. In oneembodiment, the mixture is held at about room temperature (20° C. to 25°C.).

In some embodiments, the molar ratio of gallium halide to AIGS cores isfrom about 0.1 to about 30.

In a further embodiment, the AIGS nanostructures are isolated, e.g., byprecipitation. In some embodiments, the AIGS nanostructures areprecipitated by addition of a non-solvent for the AIGS nanostructures.In some embodiments, the non-solvent is a toluene/ethanol mixture. Theprecipitated nanostructures may be further isolated by centrifugationand/or washing with a non-solvent for the nanostructures.

Also provided are methods of making nanostructures, comprising:

(a) preparing a mixture comprising AIGS nanostructures, a sulfur source,and a ligand;

(b) adding the mixture obtained in (a) to a mixture of a GaX₃ (X=F, Cl,or Br) and an oxygen-free ligand at a temperature of 180-300° C. to giveion-exchanged nanostructures with a gradient of gallium from the surfaceto the center of the nanostructures; and

(d) isolating the nanostructures.

In some embodiments, the nanostructures have a PWL of 480-545 nm.

In some embodiments, the preparing in (a) is under oxygen-freeconditions. In some embodiments, the preparing in (a) is in a glovebox.

In some embodiments, the adding in (b) is under oxygen-free conditions.In some embodiments, the adding in (b) is in a glovebox.

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 9000 of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission.

Examples of ligands are disclosed in U.S. Pat. Nos. 7,572,395,8,143,703, 8,425,803, 8,563,133, 8,916,064, 9,005,480, 9,139,770, and9,169,435, and in U.S. Patent Application Publication No. 2008/0118755.In some embodiments, the ligand in (a) is an oxygen-free ligand. In someembodiments, the ligand in (b) is an oxygen-free ligand. In someembodiments, the ligand in (a) and (b) is an alkyl amine. In someembodiments, the ligand is an alkyl amine selected from the groupconsisting of dodecylamine, oleylamine, hexadecylamine, dioctylamine,and octadecylamine. In some embodiments, the ligand in (a) isoleylamine. In some embodiments, the ligand in (b) is oleylamine. Insome embodiments, the ligand in (a) and (b) is oleylamine.

In one embodiment, the sulfur source is derived from S₈.

In one embodiment, the temperature in (a) and (b) is about 270° C.

In some embodiments, the mixture in (b) further comprises a solvent. Insome embodiments, the solvent is trioctylphosphine, dibenzyl ether, orsqualane.

In some embodiments, the GaX₃ is gallium chloride, gallium fluoride, orgallium iodide. In some embodiments, the GaX₃ is gallium chloride. Insome embodiments, the GaX₃ is Ga(III) chloride.

In some embodiments, the ratio of GaX₃ to AIGS cores is 0.008-0.2 mmolGaX₃ per mg AIGS. In some embodiments, the molar ratio of GaX₃ to AIGScores is from about 0.1 to about 30. In some embodiments, the ratio ofGaX₃ to AIGS cores is about 0.04 mmol GaX₃ per mg AIGS.

In some embodiments, the AIGS nanostructures are isolated, e.g., byprecipitation. In some embodiments, the AIGS nanostructures areprecipitated by addition of a non-solvent for the AIGS nanostructures.In some embodiments, the non-solvent is a toluene/ethanol mixture. Theprecipitated nanostructures may be further isolated by centrifugationand/or washing with a non-solvent for the nanostructures.

In some embodiments, the mixture in (a) is held at 20° C. to 100° C. Insome embodiments, the mixture in (a) is held at about room temperature(20° C. to 25° C.).

In some embodiments, the mixture in (b) is held at 200° C. to 300° C.for 0.1 hour to 200 hours. In some embodiments, the mixture in (b) isheld at 200° C. to 300° C. for about 20 hours.

Doped AIGS Nanostructures

In some embodiments, the AIGS nanostructures are doped. In someembodiments, the dopant of the nanocrystal core comprises a metal,including one or more transition metals. In some embodiments, the dopantis a transition metal selected from the group consisting of Ti, Zr, Hf,V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt,Cu, Ag, Au, and combinations thereof. In some embodiments, the dopantcomprises a non-metal. In some embodiments, the dopant is ZnS, ZnSe,ZnTe, CdSe, CdS, CdTe, HgS, HgSe, HgTe, CuInS₂, CuInSe₂, AlN, AlP, AlAs,GaN, GaP, or GaAs.

In some embodiments, the core is purified by precipitation from anon-solvent. In some embodiments, the AIGS nanostructures are filteredto remove precipitate from the core solution.

Nanostructure Compositions

In some embodiments, the present disclosure provides a nanostructurecomposition comprising:

(a) at least one population of AIGS nanostructures; and

(b) at least one organic resin.

In some embodiments, the nanostructures have a PWL between 480-545 nm.

In some embodiments, at least 80% of the nanostructure emission isband-edge emission. In other embodiments, at least 90% of the emissionis band-edge emission. In other embodiments, at least 95% of theemission is band-edge emission. In some embodiments, 92-98% of theemission is band-edge emission. In some embodiments, 93-96% of theemission is band-edge emission.

In some embodiments, the nanostructure composition further comprises atleast one second population of nanostructures. The nanostructures havinga PWL between 480-545 nm emit green light. Additional populations ofnanostructures may be added that emit in the green, yellow, orange,and/or red regions of the spectrum. These nanostructures have a PWLgreater than 545 nm. In some embodiments, the nanostructures have a PWLbetween 550-750 nm. The size of the nanostructures determines theemission wavelength. The at least one second population ofnanostructures may comprise a Group III-V nanocrystal selected from thegroup consisting of BN, BP, BAs, BSb, AlN, AlP, AlAs, AlSb, GaN, GaP,GaAs, GaSb, InN, InP, InAs, and InSb. In some embodiments, the core ofthe second population of nanostructures is an InP nanocrystal.

Organic Resin

In some embodiments, the organic resin is a thermosetting resin or anultraviolet (UV) curable resin. In some embodiments, the organic resinis cured by a method that facilitates roll-to-roll processing.

Thermosetting resins require curing in which they undergo anirreversible molecular cross-linking process which renders the resininfusible. In some embodiments, the thermosetting resin is an epoxyresin, a phenolic resin, a vinyl resin, a melamine resin, a urea resin,an unsaturated polyester resin, a polyurethane resin, an allyl resin, anacrylic resin, a polyamide resin, a polyamide-imide resin, a phenolaminecondensation polymerization resin, a urea melamine condensationpolymerization resin, or combinations thereof.

In some embodiments, the thermosetting resin is an epoxy resin. Epoxyresins are easily cured without evolution of volatiles or by-products bya wide range of chemicals. Epoxy resins are also compatible with mostsubstrates and tend to wet surfaces easily. See Boyle, M. A., et al.,“Epoxy Resins,” Composites, Vol. 21, ASM Handbook, pages 78-89 (2001).

In some embodiments, the organic resin is a silicone thermosettingresin. In some embodiments, the silicone thermosetting resin is OE6630Aor OE6630B (Dow Corning Corporation, Auburn, Mich.).

In some embodiments, a thermal initiator is used. In some embodiments,the thermal initiator is AIBN [2,2′-Azobis(2-methylpropionitrile)] orbenzoyl peroxide.

UV curable resins are polymers that cure and quickly harden when exposedto a specific light wavelength. In some embodiments, the UV curableresin is a resin having as a functional group a radical-polymerizationgroup such as a (meth)acrylyloxy group, a vinyloxy group, a styrylgroup, or a vinyl group; a cation-polymerizable group such as an epoxygroup, a thioepoxy group, a vinyloxy group, or an oxetanyl group. Insome embodiments, the UV curable resin is a polyester resin, a polyetherresin, a (meth)acrylic resin, an epoxy resin, a urethane resin, an alkydresin, a spiroacetal resin, a polybutadiene resin, or a polythiolpolyeneresin.

In some embodiments, the UV curable resin is selected from the groupconsisting of isobornyl acrylate, isobornyl methacrylate, phenoxyethylacrylate, phenoxyethyl methacrylate, urethane acrylate, allyloxylatedcyclohexyl diacrylate, bis(acryloxy ethyl)hydroxyl isocyanurate,bis(acryloxy neopentylglycol)adipate, bisphenol A diacrylate, bisphenolA dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanedioldimethacrylate, 1,3-butyleneglycol diacrylate, 1,3-butyleneglycoldimethacrylate, dicyclopentanyl diacrylate, diethyleneglycol diacrylate,diethyleneglycol dimethacrylate, dipentaerythritol hexaacrylate,dipentaerythritol monohydroxy pentaacrylate, di(trimethylolpropane)tetraacrylate, ethyleneglycol dimethacrylate, glycerol methacrylate,1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate,neopentylglycol dimethacrylate, neopentylglycol hydroxypivalatediacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate,phosphoric acid dimethacrylate, polyethyleneglycol diacrylate,polypropyleneglycol diacrylate, tetraethyleneglycol diacrylate,tetrabromobisphenol A diacrylate, triethyleneglycol divinylether,triglycerol diacrylate, trimethylolpropane triacrylate,tripropyleneglycol diacrylate, tris(acryloxyethyl)isocyanurate,phosphoric acid triacrylate, phosphoric acid diacrylate, acrylic acidpropargyl ester, vinyl terminated polydimethylsiloxane, vinyl terminateddiphenylsiloxane-dimethylsiloxane copolymer, vinyl terminatedpolyphenylmethylsiloxane, vinyl terminatedtrifluoromethylsiloxane-dimethylsiloxane copolymer, vinyl terminateddiethylsiloxane-dimethylsiloxane copolymer, vinylmethylsiloxane,monomethacryloyloxypropyl terminated polydimethyl siloxane, monovinylterminated polydimethyl siloxane, monoallyl-mono trimethylsiloxyterminated polyethylene oxide, and combinations thereof.

In some embodiments, the UV curable resin is a mercapto-functionalcompound that can be cross-linked with an isocyanate, an epoxy, or anunsaturated compound under UV curing conditions. In some embodiments,the polythiol is pentaerythritol tetra(3-mercapto-propionate) (PETMP);trimethylol-propane tri(3-mercapto-propionate) (TMPMP); glycoldi(3-mercapto-propionate) (GDMP);tris[25-(3-mercapto-propionyloxy)ethyl]isocyanurate (TEMPIC);di-pentaerythritol hexa(3-mercapto-propionate) (Di-PETMP); ethoxylatedtrimethylolpropane tri(3-mercapto-propionate) (ETTMP 1300 and ETTMP700); polycaprolactone tetra(3-mercapto-propionate) (PCL4MP 1350);pentaerythritol tetramercaptoacetate (PETMA); trimethylol-propanetrimercaptoacetate (TMPMA); or glycol dimercaptoacetate (GDMA). Thesecompounds are sold under the trade name THIOCURE® by Bruno Bock,Marschacht, Germany.

In some embodiments, the UV curable resin is a polythiol. In someembodiments, the UV curable resin is a polythiol selected from the groupconsisting of ethylene glycol bis (thioglycolate), ethylene glycolbis(3-mercaptopropionate), trimethylol propane tris (thioglycolate),trimethylol propane tris (3-mercaptopropionate), pentaerythritoltetrakis (thioglycolate), pentaerythritol tetrakis(3-mercaptopropionate)(PETMP), and combinations thereof. In some embodiments, the UV curableresin is PETMP.

In some embodiments, the UV curable resin is a thiol-ene formulationcomprising a polythiol and 1,3,5-Triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT). In some embodiments, the UV curable resin is athiol-ene formulation comprising PETMP and TTT.

In some embodiments, the UV curable resin further comprises aphotoinitiator. A photoinitiator initiates the crosslinking and/orcuring reaction of the photosensitive material during exposure to light.In some embodiments, the photoinitiator is acetophenone-based,benzoin-based, or thioxathenone-based.

In some embodiments, the photoinitiator is a vinyl acrylate-based resin.In some embodiments, the photoinitiator is MINS-311-RM (MinutaTechnology Co., Ltd, Korea).

In some embodiments, the photoinitiator is IRGACURE® 127, IRGACURE® 184,IRGACURE® 184D, IRGACURE® 2022, IRGACURE® 2100, IRGACURE® 250, IRGACURE®270, IRGACURE® 2959, IRGACURE® 369, IRGACURE® 369 EG, IRGACURE® 379,IRGACURE® 500, IRGACURE® 651, IRGACURE® 754, IRGACURE® 784, IRGACURE®819, IRGACURE® 819Dw, IRGACURE® 907, IRGACURE® 907 FF, IRGACURE® Oxe01,IRGACURE® TPO-L, IRGACURE® 1173, IRGACURE® 1173D, IRGACURE® 4265,IRGACURE® BP, or IRGACURE® MBF (BASF Corporation, Wyandotte, Mich.). Insome embodiments, the photoinitiator is TPO(2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide) or MBF (methylbenzoylformate).

In some embodiments, the weight percentage of the at least one organicresin in the nanostructure composition is between about 5% and about99%, about 5% and about 95%, about 5% and about 90%, about 5% and about80%, about 5% and about 70%, about 5% and about 60%, about 5% and about50%, about 5% and about 40%, about 5% and about 30%, about 5% and about20%, about 5% and about 10%, about 10% and about 99%, about 10% andabout 95%, about 10% and about 90%, about 10% and about 80%, about 10%and about 70%, about 10% and about 60%, about 10% and about 50%, about10% and about 40%, about 10% and about 30%, about 10% and about 20%,about 20% and about 99%, about 20% and about 95%, about 20% and about90%, about 20% and about 80%, about 20% and about 70%, about 20% andabout 60%, about 20% and about 50%, about 20% and about 40%, about 20%and about 30%, about 30% and about 99%, about 30% and about 95%, about30% and about 90%, about 30% and about 80%, about 30% and about 70%,about 30% and about 60%, about 30% and about 50%, about 30% and about40%, about 40% and about 99%, about 40% and about 95%, about 40% andabout 90%, about 40% and about 80%, about 40% and about 70%, about 40%and about 60%, about 40% and about 50%, about 50% and about 99%, about50% and about 95%, about 50% and about 90%, about 50% and about 80%,about 50% and about 70%, about 50% and about 60%, about 60% and about99%, about 60% and about 95%, about 60% and about 90%, about 60% andabout 80%, about 60% and about 70%, about 70% and about 99%, about 70%and about 95%, about 70% and about 90%, about 70% and about 80%, about80% and about 99%, about 80% and about 95%, about 80% and about 90%,about 90% and about 99%, about 90% and about 95%, or about 95% and about99%.

In some embodiments, the nanostructure composition further comprises atleast one monomer incorporated into the ligands coating the AIGSsurface. It has been discovered the AIGS nanostructures containing atleast one monomer incorporated into the ligands coating the AIGS surfacehave high QY, good compatibility with HDDA, a common monomer used ininkjet printable ink, and good blue light absorption.

In some embodiments, the at least one monomer is an acrylate. Examplesof acrylate monomers include, but are not limited to methylmethacrylate, ethyl methacrylate, isopropyl methacrylate, n-butylmethacrylate, isobutylmethacrylate, tert-butyl methacrylate, n-amylmethacrylate, isoamyl methacrylate, n-hexyl methacrylate, tridecylmethacrylate, stearyl methacrylate, decyl methacrylate, dodecylmethacrylate, methoxydiethylene glycol methacrylate, polypropyleneglycol monomethacrylate, phenylmethacrylate, phenoxyethyl methacrylate,tetrahydrofurfuryl methacrylate, tert-butylcyclohexyl methacrylate,behenyl methacrylate, dicyclopentanyl methacrylate,dicyclopentenyloxyethyl methacrylate, 2-ethylhexylmethacrylate, octylmethacrylate, isooctylmethacrylate, n-decyl methacrylate, isodecylmethacrylate, lauryl methacrylate, hexadecyl methacrylate, octadecylmethacrylate, benzyl methacrylate, 2-phenylethylmethacrylate,2-phenoxyethyl acrylate, ethyl acrylate, methyl acrylate, n-butylacrylate, 2-hydroxyethyl acrylate, 2-carboxyethyl acrylate, acrylicacid, ethylene glycol diacrylate, 1,3-propanediol diacrylate,1,4-bis(acryloyloxy)butane, isobornyl acrylate, tetrahydrofurfurylacrylate, cyclic trimethylolpropane formal acrylate, cyclohexylmethacrylate, and 4-tert-butylcyclohexylacrylate.

In some embodiments, the monomer is at least one of ethyl acrylate,HDDA, tetrahydrofurfuryl acrylate, tri(propylene glycol) diacrylate,1,4-bis(acryloyloxy)butane or isobornyl acrylate.

Method of Preparing AIGS Nanostructure Composition

The present disclosure provides a method of preparing a nanostructurecomposition, the method comprising:

(a) providing at least one population of AIGS nanostructures; and

(b) admixing at least one organic resin with the composition of (a).

In some embodiments, the nanostructures have a PWL of between 480-545nm, and at least about 80% of the emission is band-edge emission. Insome embodiments, at least 80% of the emission is band-edge emission. Inother embodiments, at least 90% of the emission is band-edge emission.In other embodiments, at least 95% of the emission is band-edgeemission. In some embodiments, 92-98% of the emission is band-edgeemission. In some embodiments, 93-96% of the emission is band-edgeemission.

The present disclosure also provides a method of preparing ananostructure composition, the method comprising:

(a) providing at least one population of AIGS nanostructures, andwherein the nanostructures were prepared using a GaX₃ (X=F, Cl, or Br)precursor and an oxygen-free ligand; and

(b) admixing at least one organic resin with the composition of (a).

In some embodiments, the nanostructures have a PWL of between 480-545nm, and at least about 60% of the emission is band-edge emission.

The present disclosure also provides a method of preparing ananostructure composition, the method comprising:

(a) providing at least one population of AIGS nanostructures, whereinthe nanostructures have a PWL of between 480-545 nm, wherein at leastabout 80% of the emission is band-edge emission, and wherein thenanostructures exhibit a QY of 80-99%; and

(b) admixing at least one organic resin with the composition of (a).

In some embodiments, the at least one population of nanostructures isadmixed with at least one organic resin at an agitation rate of betweenabout 100 rpm and about 10,000 rpm, about 100 rpm and about 5,000 rpm,about 100 rpm and about 3,000 rpm, about 100 rpm and about 1,000 rpm,about 100 rpm and about 500 rpm, about 500 rpm and about 10,000 rpm,about 500 rpm and about 5,000 rpm, about 500 rpm and about 3,000 rpm,about 500 rpm and about 1,000 rpm, about 1,000 rpm and about 10,000 rpm,about 1,000 rpm and about 5,000 rpm, about 1,000 rpm and about 3,000rpm, about 3,000 rpm and about 10,000 rpm, about 3,000 rpm and about10,000 rpm, or about 5,000 rpm and about 10,000 rpm.

In some embodiments, the at least one population of nanostructures isadmixed with at least one organic resin for a time of between about 10minutes and about 24 hours, about 10 minutes and about 20 hours, about10 minutes and about 15 hours, about 10 minutes and about 10 hours,about 10 minutes and about 5 hours, about 10 minutes and about 1 hour,about 10 minutes and about 30 minutes, about 30 minutes and about 24hours, about 30 minutes and about 20 hours, about 30 minutes and about15 hours, about 30 minutes and about 10 hours, about 30 minutes andabout 5 hours, about 30 minutes and about 1 hour, about 1 hour and about24 hours, about 1 hour and about 20 hours, about 1 hour and about 15hours, about 1 hour and about 10 hours, about 1 hour and about 1 hours,about 5 hours and about 24 hours, about 1 hours and about 20 hours,about 1 hours and about 15 hours, about hours and about 10 hours, about10 hours and about 24 hours, about 10 hours and about 20 hours, about 10hours and about 15 hours, about 15 hours and about 24 hours, about 15hours and about 20 hours, or about 20 hours and about 24 hours.

In some embodiments, the at least one population of nanostructures isadmixed with at least one organic resin at a temperature between about−5° C. and about 100° C., about −5° C. and about 75° C., about −5° C.and about 50° C., about −5° C. and about 23° C., about 23° C. and about100° C., about 23° C. and about 75° C., about 23° C. and about 50° C.,about 50° C. and about 100° C., about 50° C. and about 75° C., or about75° C. and about 100° C. In some embodiments, the at least one organicresin is admixed with the at least one population of nanostructures at atemperature between about 23° C. and about 50° C.

In some embodiments, if more than one organic resin is used, the organicresins are added together and mixed. In some embodiments, a firstorganic resin is mixed with a second organic resin at an agitation rateof between about 100 rpm and about 10,000 rpm, about 100 rpm and about5,000 rpm, about 100 rpm and about 3,000 rpm, about 100 rpm and about1,000 rpm, about 100 rpm and about 500 rpm, about 500 rpm and about10,000 rpm, about 500 rpm and about 5,000 rpm, about 500 rpm and about3,000 rpm, about 500 rpm and about 1,000 rpm, about 1,000 rpm and about10,000 rpm, about 1,000 rpm and about 5,000 rpm, about 1,000 rpm andabout 3,000 rpm, about 3,000 rpm and about 10,000 rpm, about 3,000 rpmand about 10,000 rpm, or about 5,000 rpm and about 10,000 rpm.

In some embodiments, a first organic resin is mixed with a secondorganic resin for a time of between about 10 minutes and about 24 hours,about 10 minutes and about 20 hours, about 10 minutes and about 15hours, about 10 minutes and about 10 hours, about 10 minutes and about 5hours, about 10 minutes and about 1 hour, about 10 minutes and about 30minutes, about 30 minutes and about 24 hours, about 30 minutes and about20 hours, about 30 minutes and about 15 hours, about 30 minutes andabout 10 hours, about 30 minutes and about 5 hours, about 30 minutes andabout 1 hour, about 1 hour and about 24 hours, about 1 hour and about 20hours, about 1 hour and about 15 hours, about 1 hour and about 10 hours,about 1 hour and about 5 hours, about 5 hours and about 24 hours, about5 hours and about 20 hours, about 5 hours and about 15 hours, about 5hours and about 10 hours, about 10 hours and about 24 hours, about 10hours and about 20 hours, about 10 hours and about 15 hours, about 15hours and about 24 hours, about 15 hours and about 20 hours, or about 20hours and about 24 hours.

In some embodiments, the AIGS nanostructures are combined with at leastone monomer incorporated into the ligands coating the AIGS surface priorto being combined with a resin. In some embodiments, the monomer is anacrylate. In some embodiments, the monomer is at least one of ethylacrylate, HDDA, tetrahydrofurfuryl acrylate, tri(propylene glycol)diacrylate, 1,4-bis(acryloyloxy)butane or isobornyl acrylate.

Properties of AIGS Nanostructures

In some embodiments, the AIGS nanostructures display a highphotoluminescence quantum yield. In some embodiments, the nanostructuresdisplay a photoluminescence quantum yield of between about 50% and about99%, about 50% and about 95%, about 50% and about 90%, about 50% andabout 85%, about 50% and about 80%, about 50% and about 70%, about 50%and about 60%, 60% and about 99%, about 60% and about 95%, about 60% andabout 90%, about 60% and about 85%, about 60% and about 80%, about 60%and about 70%, about 70% and about 99%, about 70% and about 95%, about70% and about 90%, about 70% and about 85%, about 70% and about 80%,about 80% and about 99%, about 80% and about 95%, about 80% and about90%, about 80% and about 85%, about 85% and about 99%, about 85% andabout 95%, about 80% and about 85%, about 85% and about 99%, about 85%and about 90%, about 90% and about 99%, about 90% and about 95%, orabout 95% and about 99%. In some embodiments, the nanostructures displaya photoluminescence quantum yield of between about 82% and about 96%,between about 85% and about 96%, and between about 93% and about 94%.

The photoluminescence spectrum of the nanostructures can cover a widedesired portion of the spectrum. In some embodiments, thephotoluminescence spectrum for the nanostructures have an emissionmaximum between 300 nm and 750 nm, 300 nm and 650 nm, 300 nm and 550 nm,300 nm and 450 nm, 450 nm and 750 nm, 450 nm and 650 nm, 450 nm and 550nm, 450 nm and 750 nm, 450 nm and 650 nm, 450 nm and 550 nm, 550 nm and750 nm, 550 nm and 650 nm, or 650 nm and 750 nm. In some embodiments,the photoluminescence spectrum for the nanostructures has an emissionmaximum of between 450 nm and 550 nm.

The size distribution of the nanostructures can be relatively narrow. Insome embodiments, the photoluminescence spectrum of the population ofnanostructures can have a full width at half maximum of between 10 nmand 60 nm, 10 nm and 40 nm, 10 nm and 30 nm, 10 nm and 20 nm, 20 nm and60 nm, 20 nm and 40 nm, 20 nm and 30 nm, 25 nm and 60 nm, 25 nm and 40nm, 25 nm and 30 nm, 30 nm and 60 nm, 30 nm and 40 nm, or 40 nm and 60nm. In some embodiments, the photoluminescence spectrum of thepopulation of nanostructures can have a full width at half maximum ofbetween 24 nm and 50 nm.

In some embodiments, the nanostructures emit light having a peakemission wavelength (PWL) between about 400 nm and about 650 nm, about400 nm and about 600 nm, about 400 nm and about 550 nm, about 400 nm andabout 500 nm, about 400 nm and about 450 nm, about 450 nm and about 650nm, about 450 nm and about 600 nm, about 450 nm and about 550 nm, about450 nm and about 500 nm, about 500 nm and about 650 nm, about 500 nm andabout 600 nm, about 500 nm and about 550 nm, about 550 nm and about 650nm, about 550 nm and about 600 nm, or about 600 nm and about 650 nm. Insome embodiments, the nanostructures emit light having a PWL betweenabout 500 nm and about 550 nm.

As a predictive value for blue light absorption efficiency, the opticaldensity at 450 nm on a per mass basis (OD₄₅₀/mass) can be calculated bymeasuring the optical density of a nanostructure solution in a 1 cm pathlength cuvette and dividing by the dry mass per mL of the same solutionafter removing all volatiles under vacuum (<200 mTorr) In someembodiments, the nanostructures have an optical density at 450 nm on aper mass basis (OD₄₅₀/mass) of between about 0.28/mg and about 0.5/mg,about 0.28/mg and about 0.4/mg, about 0.28/mg and about 0.35/mg, about0.28/mg and about 0.32/mg, about 0.32/mg and about 0.5/mg, about 0.32/mgand about 0.4/mg, about 0.32/mg and about 0.35/mg, about 0.35/mg andabout 0.5/mg, about 0.35/mg and about 0.4/mg, or about 0.4/mg and about0.5/mg. Films

The nanostructures of the present invention can be embedded in apolymeric matrix using any suitable method. As used herein, the term“embedded” is used to indicate that the nanostructures are enclosed orencased with the polymer that makes up the majority of the component ofthe matrix. In some embodiments, the at least one nanostructurepopulation is suitably uniformly distributed throughout the matrix. Insome embodiments, the at least one nanostructure population isdistributed according to an application-specific distribution. In someembodiments, the nanostructures are mixed in a polymer and applied tothe surface of a substrate.

In some embodiments, the present disclosure provides a nanostructurefilm layer comprising:

(a) a composition comprising at least one population of AIGSnanostructures and at least one ligand bound to the nanostructures; and

(b) at least one organic resin.

In some embodiments, a fraction of the ligands is bound to thenanostructures. In other embodiments, the nanostructure surfaces aresaturated with the ligands.

In some embodiments, the nanostructures have a PWL between 480 and 545nm.

In some embodiments, the composition comprising at least one populationof AIGS nanostructures further comprises at least one monomerincorporated into the ligands coating the AIGS surface. In someembodiments, the at least one monomer is an acrylate. In someembodiments, the monomer is at least one of ethyl acrylate, HDDA,tetrahydrofurfuryl acrylate, tri(propylene glycol) diacrylate,1,4-bis(acryloyloxy)butane or isobornyl acrylate.

The present disclosure also provides a method of preparing ananostructure film layer comprising:

(a) providing at least one population of AIGS nanostructures; and

(b) admixing at least one organic resin with the composition of (a).

In some embodiments, the nanostructures have a PWL of between 480-545nm.

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 90% of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission. In some embodiments, 92-98% of the emission isband-edge emission. In some embodiments, 93-96% of the emission isband-edge emission.

In some embodiments, the nanostructure composition further comprises anamino ligand having Formula I:

wherein:

x is 1 to 100;

y is 0 to 100; and

R² is C₁₋₂₀ alkyl.

In some embodiments, x is 1 to 100, 1 to 50, 1 to 20, 1 to 10, 1 to 5, 5to 100, 5 to 50, 5 to 20, 5 to 10, 10 to 100, 10 to 50, 10 to 20, 20 to100, 20 to 50, or 50 to 100. In some embodiments, x is 10 to 50. In someembodiments, x is 10 to 20. In some embodiments, x is 1. In someembodiments, x is 19. In some embodiments, x is 6. In some embodiments,x is 10.

In some embodiments, R² is C₁₋₂₀ alkyl. In some embodiments, R² is C₁₋₁₀alkyl. In some embodiments, R² is C₁₋₅ alkyl. In some embodiments, R² is—CH₂CH₃.

In some embodiments, the compound of Formula I is a commerciallyavailable amine-terminated polymer from Huntsman PetrochemicalCorporation. In some embodiments, the amine-terminated polymer offormula (VI) has x=1, y=9, and R²=—CH₃ and is JEFFAMINE M-600 (HuntsmanPetrochemical Corporation, Texas). JEFFAMINE M-600 has a molecularweight of approximately 600. In some embodiments, the amine-terminatedpolymer of formula (III) has x=19, y=3, and R² 32 —CH₃ and is JEFFAMINEM-1000 (Huntsman Petrochemical Corporation, Texas). JEFFAMINE M-1000 hasa molecular weight of approximately 1,000. In some embodiments, theamine-terminated polymer of formula (III) has x=6, y=29, and R² 32 —CH₃and is JEFFAMINE M-2005 (Huntsman Petrochemical Corporation, Texas).JEFFAMINE M-2005 has a molecular weight of approximately 2,000. In someembodiments, the amine-terminated polymer of formula (III) has x=31,y=10, and R² 32 —CH₃ and is JEFFAMINE M-2070 (Huntsman PetrochemicalCorporation, Texas). JEFFAMINE M-2070 has a molecular weight ofapproximately 2,000. In another embodiment, the ligand is a polyethyleneglycol amine available from CreativePEGWorks such as PEG550-amine andPEG350-amine.

In some embodiments, the nanostructure film layer is a color conversionlayer.

The nanostructure composition can be deposited by any suitable methodknown in the art, including but not limited to painting, spray coating,solvent spraying, wet coating, adhesive coating, spin coating,tape-coating, roll coating, flow coating, inkjet vapor jetting, dropcasting, blade coating, mist deposition, or a combination thereof. Insome embodiments, the nanostructure composition is cured afterdeposition. Suitable curing methods include photo-curing, such as UVcuring, and thermal curing. Traditional laminate film processingmethods, tape-coating methods, and/or roll-to-roll fabrication methodscan be employed in forming the nanostructure films of the presentinvention. The nanostructure composition can be coated directly onto thedesired layer of a substrate. Alternatively, the nanostructurecomposition can be formed into a solid layer as an independent elementand subsequently applied to the substrate. In some embodiments, thenanostructure composition can be deposited on one or more barrierlayers.

Spin Coating

In some embodiments, the nanostructure composition is deposited onto asubstrate using spin coating. In spin coating a small amount of materialis typically deposited onto the center of a substrate loaded a machinecalled the spinner which is secured by a vacuum. A high speed ofrotation is applied on the substrate through the spinner which causescentripetal force to spread the material from the center to the edge ofthe substrate. While most of the material would be spun off, a certainamount remains on the substrate, forming a thin film of material on thesurface as the rotation continues. The final thickness of the film isdetermined by the nature of the deposited material and the substrate inaddition to the parameters chosen for the spin process such as spinspeed, acceleration, and spin time. For typical films, a spin speed of1500 to 6000 rpm is used with a spin time of 10-60 seconds. In someembodiments, films are deposited at very low speeds, e.g., less than1000 rpm. In some embodiments, the films are cast at about 300, about400, about 500, about 600, about 700, about 800 or about 900 rpm.

Mist Deposition

In some embodiments, the nanostructure composition is deposited onto asubstrate using mist deposition. Mist deposition takes place at roomtemperature and atmospheric pressure and allows precise control overfilm thickness by changing the process conditions. During mistdeposition, a liquid source material is turned into a very fine mist andcarried to the deposition chamber by nitrogen gas. The mist is thendrawn to the wafer surface by a high voltage potential between the fieldscreen and the wafer holder. Once the droplets coalesce on the wafersurface, the wafer is removed from the chamber and thermally cured toallow the solvent to evaporate. The liquid precursor is a mixture ofsolvent and material to be deposited. It is carried to the atomizer bypressurized nitrogen gas. Price, S. C., et al., “Formation of Ultra-ThinQuantum Dot Films by Mist Deposition,” ESC Transactions 11:89-94 (2007).

Spray Coating

In some embodiments, the nanostructure composition is deposited onto asubstrate using spray coating. The typical equipment for spray coatingcomprises a spray nozzle, an atomizer, a precursor solution, and acarrier gas. In the spray deposition process, a precursor solution ispulverized into micro sized drops by means of a carrier gas or byatomization (e.g., ultrasonic, air blast, or electrostatic). Thedroplets that come out of the atomizer are accelerated by the substratesurface through the nozzle by help of the carrier gas which iscontrolled and regulated as desired. Relative motion between the spraynozzle and the substrate is defined by design for the purpose of fullcoverage on the substrate.

In some embodiments, application of the nanostructure compositionfurther comprises a solvent. In some embodiments, the solvent forapplication of the nanostructure composition is water, organic solvents,inorganic solvents, halogenated organic solvents, or mixtures thereof.Illustrative solvents include, but are not limited to, water, D₂O,acetone, ethanol, dioxane, ethyl acetate, methyl ethyl ketone,isopropanol, anisole, γ-butyrolactone, dimethylformamide,N-methylpyrroldinone, dimethylacetamide, hexamethylphosphoramide,toluene, dimethylsulfoxide, cyclopentanone, tetramethylene sulfoxide,xylene, ε-caprolactone, tetrahydrofuran, tetrachloroethylene,chloroform, chlorobenzene, dichloromethane, 1,2-dichloroethane,1,1,2,2-tetrachloroethane, or mixtures thereof.

Ink-Jet Printing

Solvents suitable for inkjet printing of nanostructures are known tothose of skill in the art. In some embodiments, the organic solvent is asubstituted aromatic or heteroaromatic solvent described in U.S. PatentAppl. Publication No. 2018/0230321, which is incorporated herein byreference in its entirety.

In some embodiments, the organic solvent used in a nanostructurecomposition used as an inkjet printing formulation is defined by itsboiling point, viscosity, and surface tension. Properties of organicsolvents suitable for inkjet printing formulations are shown in TABLE 1.

TABLE 1 Properties of organic solvents for inkjet printing formulationsBoiling Surface Point Viscosity tension Solvent (° C.) (mPa · s)(dyne/cm) 1-Methylnaphthalene 240 3.3 38 1-Methoxynaphthalene 270 7.2 433-Phenoxytoluene 271 4.8 37 Dibenzyl ether 298 8.7 39 Benzyl benzoate324 10.0  44 Butyl benzoate 249 2.7 34 Hexyl benzoate 272 — —Octylbenzene 265 2.6 31 Cyclohexylbenzene 240 2.0 34 Hexadecane 287 3.428 4-Methylanisole 179 — 29

In some embodiments, the organic solvent has a boiling point at 1atmosphere of between about 150° C. and about 350° C. In someembodiments the organic solvent has a boiling point at 1 atmosphere ofbetween about 150° C. and about 350° C., about 150° C. and about 300°C., about 150° C. and about 250° C., about 150° C. and about 200° C.,about 200° C. and about 350° C., about 200° C. and about 300° C., about200° C. and about 250° C., about 250° C. and about 350° C., about 250°C. and about 300° C., or about 300° C. and about 350° C.

In some embodiments, the organic solvent has a viscosity between about 1mPa·s and about 15 mPa·s. In some embodiments, the organic solvent has aviscosity between about 1 mPa·s and about 15 mPa·s, about 1 mPa·s andabout 10 mPa·s, about 1 mPa·s and about 8 mPa·s, about 1 mPa·s and about6 mPa·s, about 1 mPa·s and about 4 mPa·s, about 1 mPa·s and about 2mPa·s, about 2 mPa·s and about 15 mPa·s, about 2 mPa·s and about 10mPa·s, about 2 mPa·s and about 8 mPa·s, about 2 mPa·s and about 6 mPa·s,about 2 mPa·s and about 4 mPa·s, about 4 mPa·s and about 15 mPa·s, about4 mPa·s and about 10 mPa·s, about 4 mPa·s and about 8 mPa·s, about 4mPa·s and about 6 mPa·s, about 6 mPa·s and about 15 mPa·s, about 6 mPa·sand about 10 mPa·s, about 6 mPa·s and about 8 mPa·s, about 8 mPa·s andabout 15 mPa·s, about 8 mPa·s and about 10 mPa·s, or about 10 mPa·s andabout 15 mPa·s.

In some embodiments, the organic solvent has a surface tension ofbetween about 20 dyne/cm and about 50 dyne/cm. In some embodiments, theorganic solvent has a surface tension of between about 20 dyne/cm andabout 50 dyne/cm, about 20 dyne/cm and about 40 dyne/cm, about 20dyne/cm and about 35 dyne/cm, about 20 dyne/cm and about 30 dyne/cm,about 20 dyne/cm and about 25 dyne/cm, about 25 dyne/cm and about 50dyne/cm, about 25 dyne/cm and about 40 dyne/cm, about 25 dyne/cm andabout 35 dyne/cm, about 25 dyne/cm and about 30 dyne/cm, about 30dyne/cm and about 50 dyne/cm, about 30 dyne/cm and about 40 dyne/cm,about 30 dyne/cm and about 35 dyne/cm, about 35 dyne/cm and about 50dyne/cm, about 35 dyne/cm and about 40 dyne/cm, or about 40 dyne/cm andabout 50 dyne/cm.

In some embodiments, the organic solvent used in the nanostructurecomposition is an alkylnaphthalene, an alkoxynaphthalene, analkylbenzene, an aryl, an alkyl-substituted benzene, acycloalkylbenzene, a C₉-C₂₀ alkane, a diarylether, an alkyl benzoate, anaryl benzoate, or an alkoxy-substituted benzene.

In some embodiments, the organic solvent used in a nanostructurecomposition is 1-tetralone, 3-phenoxytoluene, acetophenone,1-methoxynaphthalene, n-octylbenzene, n-nonylbenzene, 4-methylanisole,n-decylbenzene, p-diisopropylbenzene, pentylbenzene, tetralin,cyclohexylbenzene, chloronaphthalene, 1,4-dimethylnaphthalene,3-isopropylbiphenyl, p-methylcumene, dipentylbenzene, o-diethylbenzene,m-diethylbenzene, p-diethylbenzene, 1,2,3,4-tetramethylbenzene,1,2,3,5-tetramethylbenzene, 1,2,4,5-tetrametylbenzene, butylbenzene,dodecylbenzene, 1-methylnaphthalene, 1,2,4-trichlorobenzene, diphenylether, diphenylmethane, 4-isopropylbiphenyl, benzyl benzoate,1,2-bi(3,4-dimethylphenyl)ethane, 2-isopropylnaphthalene, dibenzylether, or a combination thereof. In some embodiments, the organicsolvent used in a nanostructure composition is 1-methylnaphthalene,n-octylbenzene, 1-methoxynapththalene, 3-phenoxytoluene,cyclohexylbenzene, 4-methylanisole, n-decylbenzene, or a combinationthereof.

In some embodiments, the organic solvent is an anhydrous organicsolvent. In some embodiments, the organic solvent is a substantiallyanhydrous organic solvent.

In some embodiments, the organic solvent is a non-volatile monomer orcombination of monomers chosen from the list presented above.

In some embodiments, the weight percentage of organic solvent in thenanostructure composition is between about 70% and about 99%. In someembodiments, the weight percentage of organic solvent in thenanostructure composition is between about 70% and about 99%, about 70%and about 98%, about 70% and about 95%, about 70% and about 90%, about70% and about 85%, about 70% and about 80%, about 70% and about 75%,about 75% and about 99%, about 75% and about 98%, about 75% and about95%, about 75% and about 90%, about 75% and about 85%, about 75% andabout 80%, about 80% and about 99%, about 80% and about 98%, about 80%and about 95%, about 80% and about 90%, about 80% and about 85%, about85% and about 99%, about 85% and about 98%, about 85% and about 95%,about 85% and about 90%, about 90% and about 99%, about 90% and about98%, about 90% and about 95%, about 95% and about 99%, about 95% andabout 98%, or about 98% and about 99%. In some embodiments, the weightpercentage of organic solvent in the nanostructure composition isbetween about 95% and about 99%.

In some embodiments, the composition for inkjet printing furthercomprises a monomer incorporated into the ligands coating the AIGSsurface. In some embodiments, the monomer is an acrylate. In someembodiments, the monomer is at least one of ethyl acrylate, HDDA,tetrahydrofurfuryl acrylate, tri(propylene glycol) diacrylate, 1,4-bis(aincorporated into the ligands coating the AIGS surface ryloyloxy)butaneor isobornyl acrylate. It has been found that use of a monomer in theinkjet composition provides for better compatibility of the AIGSnanostructures in the inkjet composition, improves QY, and improves bluelight absorption.

Film Curing

In some embodiments, the compositions are thermally cured to form thenanostructure layer. In some embodiments, the compositions are curedusing UV light. In some embodiments, the nanostructure composition iscoated directly onto a barrier layer of a nanostructure film, and anadditional barrier layer is subsequently deposited upon thenanostructure layer to create the nanostructure film. A supportsubstrate can be employed beneath the barrier film for added strength,stability, and coating uniformity, and to prevent materialinconsistency, air bubble formation, and wrinkling or folding of thebarrier layer material or other materials. Additionally, one or morebarrier layers are may be deposited over a nanostructure layer to sealthe material between the top and bottom barrier layers. Suitably, thebarrier layers can be deposited as a laminate film and optionally sealedor further processed, followed by incorporation of the nanostructurefilm into the particular lighting device. The nanostructure compositiondeposition process can include additional or varied components, as willbe understood by persons of ordinary skill in the art. Such embodimentswill allow for in-line process adjustments of the nanostructure emissioncharacteristics, such as brightness and color (e.g., to adjust thequantum film white point), as well as the nanostructure film thicknessand other characteristics. Additionally, these embodiments will allowfor periodic testing of the nanostructure film characteristics duringproduction, as well as any necessary toggling to achieve precisenanostructure film characteristics. Such testing and adjustments canalso be accomplished without changing the mechanical configuration ofthe processing line, as a computer program can be employed toelectronically change the respective amounts of mixtures to be used informing a nanostructure film.

It has been discovered that nanostructure films with high PCE can beobtained when the film is processed without exposure of the AIGSnanocrystals to blue or UV light prior to providing an oxygen-freeenvironment for the nanostructures. The oxygen-free environment can beprovided by:

(a) encapsulating the films with an oxygen barrier before thermalprocessing and/or exposure to blue light for PCE measurement;

(b) use of oxygen reactive materials as part of the formulation duringthermal processing or light exposure; and/or

(c) temporary blocking of oxygen through the use of a sacrificialbarrier layer.

In some embodiments, improvement in PCE can be achieved by any methodthat can form an oxygen barrier on the AIGS layer. In mass production ofdevices containing these AIGS-CC layers, the encapsulation may becarried out using vapor deposition processes. A typical process flow inthis case comprises inkjet printing of the AIGS layer, followed bycuring with UV irradiation, baking at 180° C. to remove volatiles,deposition of an organic planarization layer, then deposition of aninorganic barrier layer. Techniques used for deposition of the inorganiclayer may include atomic layer deposition (ALD), molecular layerdeposition (MLD), chemical vapor deposition (CVD) (with or withoutplasma enhancement), pulsed vapor deposition (PVD), sputtering, or metalevaporation. Other potential encapsulation methods include solutionprocessed or printed organic layers, UV or thermally curable adhesives,lamination using barrier films, etc.

In some embodiments, the films are encapsulated in an inert atmosphere.In some embodiments, the films are encapsulated in a nitrogen or argonatmosphere.

Oxygen reactive materials include any materials that are more reactiveto oxygen than are AIGS nanostructures. Examples of oxygen reactivematerials include, without limitation phosphines, phosphites,metal-organic precursors, titanium nitride, and tantalum nitride. Insome embodiments, the phosphines may be any one of the C₁₋₂₀trialkylphosphines. In one embodiment, the phosphine istrioctylphosphine. In some embodiments, the phosphites may betrialkylphosphites, alkylarylphosphites or triarylphosphites. In someembodiments, the metal-organic precursors may be trialkylaluminum,trialkylgallium, trialkylindium, dialkylzine, etc.

Examples of sacrificial barrier layers include polymer layers that canbe dissolved in and washed away in a solvent. Examples of such polymersinclude, but are not limited to polyvinyl alcohol, polyvinyl acetate,and polyethylene glycols. Other examples of sacrificial barrier layersinclude inorganic compounds or salts such as lithium silicate, lithiumfluoride, etc. Examples of solvents that can be used to wash away thesacrificial layer include water, and organic solvents such as alcohols(e.g., ethanol, methanol), halocarbons (e.g., methylene chloride andethylene chloride), aromatic hydrocarbons (e.g, toluene, xylene),aliphatic hydrocarbons (e.g, hexane, octane, octadecene)tetrahydrofuran, C₄₋₂₀ eithers such as diethyl ether, and C₂₋₂₀ esterssuch as ethyl acetate.

Nanostructure Film Features and Embodiments

In some embodiments, the nanostructure films of the present inventionare used to form display devices. As used herein, a display devicerefers to any system with a lighting display. Such devices include, butare not limited to, devices encompassing a liquid crystal display (LCD),televisions, computers, mobile phones, smart phones, personal digitalassistants (PDAs), gaming devices, electronic reading devices, digitalcameras, augmented reality/virtual reality (AR/VR) glasses, lightprojection systems, head-up displays, and the like.

In some embodiments, the nanostructure films are part of a nanostructurecolor conversion layer.

In some embodiments, the display device comprises a nanostructure colorconverter. In some embodiments, the display device comprises a backplane; a display panel disposed on the back plane; and a nanostructurelayer. In some embodiments, the nanostructure layer is disposed on thedisplay panel. In some embodiments, the nanostructure layer comprises apatterned nanostructure layer.

In some embodiments, the backplane comprises a blue LED, an LCD, anOLED, or a microLED.

In some embodiments, the nanostructure layer is disposed on the lightsource element. In some embodiments, the nanostructure layer comprises apatterned nanostructure layer. The patterned nanostructure layer may beprepared by any known method in the art. In one embodiment, thepatterned nanostructure layer is prepared by ink-jet printing of asolution of the nanostructures. Suitable solvents for the solutioninclude, without limitation, dipropylene glycol monomethyl ether acetate(DPMA), polyglycidyl methacrylate (PGMA), diethylene glycol monoethylether acetate (EDGAC), and propylene glycol methyl ether acetate(PGMEA). Volatile solvents may also be used in inkjet printing becausethey allow for rapid drying. Volatile solvents include ethanol,methanol, 1-propanol, 2-propanol, acetone, methyl ethyl ketone, methylisobutyl ketone, ethyl acetate, and tetrahydrofuran. Alternatively, a“solvent-free” ink, in which the AIGS nanostructures are dispersed inthe ink monomers, may be used for inkjet printing.

In some embodiments, the AIGS nanostructures are inkjet printed with acomposition also comprising at least one monomer incorporated into theligands coating the AIGS surface. In some embodiments, the at least onemonomer is an acrylate. In some embodiments, the acrylate is at leastone of ethyl acrylate, tetrahydrofurfuryl acrylate, tri(propyleneglycol) diacrylate, 1,4-bis(acryloyloxy)butane or isobornyl acrylate. Ithas been discovered that AIGS nanostructures treated with at least onemonomer during ligand exchange provides better compatibility with HDDA,a common monomer used in inkjet printable ink, improves QY, and bluelight absorption.

In some embodiments, the nanostructure layer has a thickness betweenabout 1 μm and about 25 μm. In some embodiments, the nanostructure layerhas a thickness between about 5 μm and about 25 μm. In some embodiments,the nanostructure layer has a thickness between about 10 μm and about 12μm.

In some embodiments, the nanostructure display device exhibits a PCE ofat least 32%. In some embodiments, the nanostructure molded articleexhibits a PCE of 32-40%. In some embodiments, the nanostructure moldedarticle exhibits a PCE of 33-40%, 34-40%, 35-40%, 36-40%, 37-40%,38-40%, 39-40%, 33-39%, 34-39%, 35-39%, 36-39%, 37-39%, 38-39%, 33-38%,34-38%, 35-38%, 36-38%, 37-38%, 33-37%, 34-37%, 35-37%, 36-37%, 33-36%,34-36%, 35-36%, 33-35%, or 34-35%.

In some embodiments, the optical films comprising a nanostructure layerare substantially free of cadmium. As used herein, the term“substantially free of cadmium” is intended that the nanostructurecompositions contain less than 100 ppm by weight of cadmium. The RoHScompliance definition requires that there should be no more than 0.01%(100 ppm) by weight of cadmium in the raw homogeneous precursormaterials. The cadmium concentration can be measured by inductivelycoupled plasma mass spectroscopy (ICP-MS) analysis, and are on the partsper billion (ppb) level. In some embodiments, optical films that are“substantially free of cadmium” contain 10 to 90 ppm cadmium. In otherembodiment, optical films that are substantially free of cadmium containless than about 50 ppm, less than about 20 ppm, less than about 10 ppm,or less than about 1 ppm of cadmium.

Nanostructure Molded Article

In some embodiments, the present disclosure provides a nanostructuremolded article comprising:

(a) a first barrier layer;

(b) a second barrier layer; and

(c) a nanostructure layer between the first barrier layer and the secondbarrier layer, wherein the nanostructure layer comprises a population ofnanostructures comprising AIGS nanostructures; and at least one organicresin.

In some embodiments, the nanostructures have a PWL between 480-545 nm.

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 90% of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission. In some embodiments, 92-98% of the emission isband-edge emission. In some embodiments, 93-96% of the emission isband-edge emission. In some embodiments, the nanostructure moldedarticle exhibits a PCE of at least 32%. In some embodiments, thenanostructure molded article exhibits a PCE of 32-40%. In someembodiments, the nanostructure molded article exhibits a PCE of 33-40%,34-40%, 35-40%, 36-40%, 37-40%, 38-40%, 39-40%, 33-39%, 34-39%, 35-39%,36-39%, 37-39%, 38-39%, 33-38%, 34-38%, 35-38%, 36-38%, 37-38%, 33-37%,34-37%, 35-37%, 36-37%, 33-36%, 34-36%, 35-36%, 33-35%, or 34-35%.

Barrier Layers

In some embodiments, the nanostructure molded article comprises one ormore barrier layers disposed on either one or both sides of thenanostructure layer. Suitable barrier layers protect the nanostructurelayer and the nanostructure molded article from environmental conditionssuch as high temperatures, oxygen, and moisture. Suitable barriermaterials include non-yellowing, transparent optical materials which arehydrophobic, chemically and mechanically compatible with thenanostructure molded article, exhibit photo- and chemical-stability, andcan withstand high temperatures. In some embodiments, the one or morebarrier layers are index-matched to the nanostructure molded article. Insome embodiments, the matrix material of the nanostructure moldedarticle and the one or more adjacent barrier layers are index-matched tohave similar refractive indices, such that most of the lighttransmitting through the barrier layer toward the nanostructure moldedarticle is transmitted from the barrier layer into the nanostructurelayer. This index-matching reduces optical losses at the interfacebetween the barrier and matrix materials.

The barrier layers are suitably solid materials, and can be a curedliquid, gel, or polymer. The barrier layers can comprise flexible ornon-flexible materials, depending on the particular application. Barrierlayers are generally planar layers, and can include any suitable shapeand surface area configuration, depending on the particular lightingapplication. In some embodiments, the one or more barrier layers will becompatible with laminate film processing techniques, whereby thenanostructure layer is disposed on at least a first barrier layer, andat least a second barrier layer is disposed on the nanostructure layeron a side opposite the nanostructure layer to form the nanostructuremolded article according to one embodiment of the present invention.Suitable barrier materials include any suitable barrier materials knownin the art. For example, suitable barrier materials include glasses,polymers, and oxides. Suitable barrier layer materials include, but arenot limited to, polymers such as polyethylene terephthalate (PET);oxides such as silicon oxide, titanium oxide, or aluminum oxide (e.g.,SiO₂, Si₂O₃, TiO₂, or Al₂O₃); and suitable combinations thereof. In someembodiments, each barrier layer of the nanostructure molded articlecomprises at least 2 layers comprising different materials orcompositions, such that the multi-layered barrier eliminates or reducespinhole defect alignment in the barrier layer, providing an effectivebarrier to oxygen and moisture penetration into the nanostructure layer.The nanostructure layer can include any suitable material or combinationof materials and any suitable number of barrier layers on either or bothsides of the nanostructure layer. The materials, thickness, and numberof barrier layers will depend on the particular application, and willsuitably be chosen to maximize barrier protection and brightness of thenanostructure layer while minimizing thickness of the nanostructuremolded article. In some embodiments, each barrier layer comprises alaminate film, in some embodiments, a dual laminate film, wherein thethickness of each barrier layer is sufficiently thick to eliminatewrinkling in roll-to-roll or laminate manufacturing processes. Thenumber or thickness of the barriers may further depend on legal toxicityguidelines in embodiments where the nanostructure s comprise heavymetals or other toxic materials, which guidelines may require more orthicker barrier layers. Additional considerations for the barriersinclude cost, availability, and mechanical strength.

In some embodiments, the nanostructure film comprises two or morebarrier layers adjacent each side of the nanostructure layer, forexample, two or three layers on each side or two barrier layers on eachside of the nanostructure layer. In some embodiments, each barrier layercomprises a thin glass sheet, e.g., glass sheets having a thickness ofabout 100 μm, 100 μm or less, or 50 μm or less.

Each barrier layer of the nanostructure film of the present inventioncan have any suitable thickness, which will depend on the particularrequirements and characteristics of the lighting device and application,as well as the individual film components such as the barrier layers andthe nanostructure layer, as will be understood by persons of ordinaryskill in the art. In some embodiments, each barrier layer can have athickness of 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less,20 μm or less, or 15 μm or less. In certain embodiments, the barrierlayer comprises an oxide coating, which can comprise materials such assilicon oxide, titanium oxide, and aluminum oxide (e.g., SiO₂, Si₂O₃,TiO₂, or Al₂O₃). The oxide coating can have a thickness of about 10 μmor less, 5 μm or less, 1 μm or less, or 100 nm or less. In certainembodiments, the barrier comprises a thin oxide coating with a thicknessof about 100 nm or less, 10 nm or less, 5 nm or less, or 3 nm or less.The top and/or bottom barrier can consist of the thin oxide coating, ormay comprise the thin oxide coating and one or more additional materiallayers.

Display Device with Nanostructure Color Conversion Layer

In some embodiments, the present invention provides a display devicecomprising:

(a) a display panel to emit a first light;

(b) a backlight unit configured to provide the first light to thedisplay panel; and

(c) a color filter comprising at least one pixel region comprising acolor conversion layer.

In some embodiments, the color filter comprises at least 1, 2, 3, 4, 5,6, 7, 8, 9, or 10 pixel regions. In some embodiments, when blue light isincident on the color filter, red light, white light, green light,and/or blue light may be respectively emitted through the pixel regions.In some embodiments, the color filter is described in U.S. Pat. No.9,971,076, which is incorporated herein by reference in its entirety.

In some embodiments, each pixel region includes a color conversionlayer. In some embodiments, a color conversion layer comprisesnanostructures described herein configured to convert incident lightinto light of a first color. In some embodiments, the color conversionlayer comprises nanostructures described herein configured to convertincident light into blue light.

In some embodiments, the display device comprises 1, 2, 3, 4, 5, 6, 7,8, 9, or 10 color conversion layers. In some embodiments, the displaydevice comprises 1 color conversion layer comprising the nanostructuresdescribed herein. In some embodiments, the display device comprises 2color conversion layers comprising the nanostructures described herein.In some embodiments, the display device comprises 3 color conversionlayers comprising the nanostructures described herein. In someembodiments, the display device comprises 4 color conversion layerscomprising the nanostructures described herein. In some embodiments, thedisplay device comprises at least one red color conversion layer, atleast one green color conversion layer, and at least one blue colorconversion layer.

In some embodiments, the color conversion layer has a thickness betweenabout 3 μm and about 10 μm, about 3 μm and about 8 μm, about 3 μm andabout 6 μm, about 6 μm and about 10 μm, about 6 μm and about 8 μm, orabout 8 μm and about 10 μm. In some embodiments, the color conversionlayer has a thickness between about 3 m and about 10 μm.

The nanostructure color conversion layer can be deposited by anysuitable method known in the art, including but not limited to painting,spray coating, solvent spraying, wet coating, adhesive coating, spincoating, tape-coating, roll coating, flow coating, inkjet printing,photoresist patterning, drop casting, blade coating, mist deposition, ora combination thereof. In some embodiments, the nanostructure colorconversion layer is deposited by photoresist patterning. In someembodiments, nanostructure color conversion layer is deposited by inkjetprinting.

Compositions Comprising AIGS Nanostructures and Ligands

In some embodiments, the AIGS nanostructure composition furthercomprises one or more ligands. The ligands include amino-ligands, polyamino-ligands, mercapto-ligands, phosphino-ligands, silane ligands, aswell as polymeric or oligomeric chains such as polyethylene glycol withamine and silane groups.

In some embodiments, the amino-ligands have Formula I:

wherein.

x is 1 to 100;

y is 0 to 100; and

R² is C₁₋₂₀ alkyl.

In some embodiments, the polyamino-ligand is a polyamino alkane, apolyamine-cycloalkane, a polyamino heterocyclic compound, a polyaminofunctionalized silicone, or polyamino substituted ethylene glycol. Insome embodiments, the polyamino-ligand is a C₂₋₂₀ alkane or C₂₋₂₀cycloalkane substituted by two or three amino groups and optionallycontaining one or two amino groups in place of a carbon group. In someembodiments, the polyamino-ligand is ethylenediamine,1,2-diaminopropane, 1,2-diamino-2-methylpropane,N-methyl-ethylenediamine, N-ethyl-ethylenediamine,N-isopropyl-ethylenediamine, N-cyclohexyl-ethylenediamine,N-cyclohexyl-ethylenediamine, N-octyl-ethylenediamine,N-decyl-ethylenediamine, N-dodecyl-ethylenediamine,N,N-dimethyl-ethylenediamine, N,N-diethyl-ethylenediamine,N,N′-diethyl-ethylenediamine, N,N′-diisopropyl ethylenediamine,N,N,N′-trimethyl-ethylenediamine, diethylenetriamine,N-isopropyl-diethylenetriamine, N-(2-aminoethyl)-1,3-propanediamine,triethylenetetramine, N,N′-bis(3-aminopropyl)ethylenediamine,N,N′-bis(2-aminoethyl)-1,3-propanediamine, tris(2-aminoethyl)amine,tetraethylenepentamine, pentaethylene hexamine,2-(2-amino-ethylamino)ethanol, N,N-bis(hydroxyethyl)ethylenediamine,N-(hydroxyethyl)diethylenetriamine,N-(hydroxyethyl)triethylenetetramine, piperazine,1-(2-aminoethyl)piperazine, 4-(2-aminoethyl)morpholine,polyethyleneimine, 1,3-diaminopropane, 1,4-diaminobutane,1,3-diaminopentane, 1,5-diminopemane, 2,2-dimethyl-1,3-propanediamine,hexamethylenediamine, 2-methyl-1,5-diaminopropane, 1,7-diaminoheptane,1,8-diaminooctane, 2,2,4-trimethyl-1,6-hexanediamine,2,4,4-trimethyl-1,6-hexanediamine, 1,9-diaminononane,1,10-diaminodecane, 1,12-diaminododecane, N-methyl-1,3-propanediamine,N-ethyl-1,3-propanediamine,N-isopropyl-1,3-propanediamine,N,N-dimethyl-1,3-propanediamine,N,N′-dimethyl-1,3-propanediamine, N,N′-diethyl-1,3-propanediamine,N,N′-diisopropyl-1,3-propanediamine,N,N,N′-trimethyl-1,3-propanediamine, 2-butyl-2-ethyl-1,5-pentanediamine,N,N′-dimethyl-1,6-hexanediamine, 3,3′-diamino-N-methyl-dipropylamine,N-(3-aminopropyl)-1,3-propanediamine, spermidine,bis(hexamethylene)triamine,N,N′,N″-trimethyl-bis(hexamethylene)triamine, 4-amino-1,8-octanediamine,N,N′-bis(3-aminopropyl)-1,3-propiediamine, spermine,4,4′-methylenebis(cyclohexylamine),1,2-diaminocyclohexane,1,4-diaminocyclohexane, 1,3-cyclohexanebis(methylamine), 1,4-cyclohexanebis(methylamine),1,2-bis(aminoethoxy)ethane, 4,9-dioxa-1,12-dodecanediamine,4,7,10-trioxa-1,13-tridecanediamine, 1,3-diamino-hydroxy-propane,4,4-methylene dipiperidine, 4-(aminomethyl)piperidine,3-(4-aminobutyl)piperidine, or polyallylamine. In some embodiments, thepolyamino-ligand is 1,3-cyclohexanebis(methylamine),2,2-dimethyl-1,3-proparnediamine, or tris(2-aminoethyl)amine.

In some embodiments, the polyamino-ligand is a polyamino heterocycliccompound. In some embodiments, the polyamino heterocyclic compound is2,4-diamino-6-phenyl-1,3,5-triazine,6-methyl-1,3,5-triazine-2,4-diamine,2,4-diamino-6-diethylamino-1,3,5-triazine,2-N,4-N,6-N-Tripropyl-1,3,5-triazine-2,4,6-triamine,2,4-diaminopyrimidine, 2,4,6-triaminopyrimidine, 2,5-diaminopyridine,2,4,5,6-tetraaminopyrimidine, pyridine-2,4,5-triamine,1-(3-aminopropyl)imidazole, 4-phenyl-1H-imidazole-1,2-diamine,1H-imidazole-2,5-diamine,4-phenyl-N(1)-[(E)-phenylmethylidene]-1H-imidazole-1,2-diamine,2-phenyl-1H-imidazole-4,5-diamine, 1H-imidazole-2,4,5-triamine,1H-pyrrole-2,5-diamine, 1,2,4,5-tetrazine-3,6-diamine,N,N′-dicyclohexyl-1,2,4,5-tetrazine-3,6-diamine,N3-propyl-1H-1,2,4-triazole-3,5-diamine, orN,N′-bis(2-methoxybenzyl)-1H-1,2,4-triazole-3,5-diamine.

In some embodiments, the polyamino-ligand is a polyamino functionalizedsilicone. In some embodiments, the polyamino functionalized silicone isone of.

In some embodiments, the polyamino-ligand is a polyamino-substitutedethylene glycol. In some embodiments, the polyamino substituted ethyleneglycol is2-[3-amino-4-[2-[2-amino-4-(2-hydroxyethyl)phenoxy]ethoxy]phenyl]ethanol,1,5-diamino-3-oxapentane, 1,8-diamino-3,6-dioxaoctane,bis[5-chloro-1H-indol-2-YL-carbonyl-aminoethyl]-ethylene glycol,amino-PEG8-t-Boc-hydrazide, or 2-(2-(2-ethoxyethoxy)ethoxy)ethanamine.

In some embodiments, the mercapto-ligands are(3-mercaptopropyl)triethoxysilane, 3,6-dioxa-1,8-octanedithiol;6-mercapto-1-hexanol; mercapto succinic acid, mercapto undecanoic acid,mercapto hexanoic acid, mercapto propioninic acid, mercapto acetic acid,cysteine, methionine, and mercapto poly(ethylene glycol).

In some embodiments, the silane-ligand is an aminoalkyltrialkoxysilaneor thioalkyltrialkoxysilane. In some embodiments, theaminoalkyltrialkoxysilane is 3-aminopropyl)triethoxysilane or3-mercapopropyl)triethoxysilane.

In some embodiments, the ligands include, but are not limited toamino-polyalkylene oxide (e.g., about m.w. 1000);(3-aminopropyl)trimethoxysilane); (3-mercaptopropyl)triethoxysilane;DL-α-lipoic acid; 3,6-dioxa-1,8-octanedithiol; 6-mercapto-1-hexanol;methoxypolyethylene glycol amine (about m.w. 500); poly(ethyleneglycol)methyl ether thiol (about m.w. 800); diethyl phenylphosphonite; dibenzylN,N-diisopropylphosphoramidite; di-tert-butylN,N-diisopropylphosphoramidite; tris(2-carboxyethyl)phosphinehydrochloride; poly(ethylene glycol) methyl ether thiol (about m.w.2000); methoxypolyethylene glycol amine (about m.w. 750); acrylamide;and polyethylenimine.

Particular combinations of ligands include amino-polyalkylene oxide(about m.w. 1000) and methoxypolyethylene glycol amine (about m.w. 500);amino-polyalkylene oxide (about m.w. 1000) and 6-mercapto-1-hexanol;amino-polyalkylene oxide (about m.w. 1000) and(3-mercaptopropyl)triethoxysilane; and 6-mercapto-1-hexanol andmethoxypolyethylene glycol amine (about m.w. 500); which providedexcellent dispersibility and thermal stability. See Example 9.

Films comprising the AIGS nanostructures and a polyamino ligand exhibithigher film photo conversion efficiency (PCE), exhibit less wrinkling,and less delamination of the films compared to AIGS-containing filmswithout a polyamino-ligand and compared to a mono-amino-ligand. Thus,compositions comprising AIGS-polyamino-ligands are uniquely suitable foruse in nanostructure color conversion layers.

The following examples are illustrative and non-limiting, of theproducts and methods described herein. Suitable modifications andadaptations of the variety of conditions, formulations, and otherparameters normally encountered in the field and which are obvious tothose skilled in the art in view of this disclosure are within thespirit and scope of the invention.

EXAMPLES Example 1: AIGS Core Synthesis

Sample ID 1 was prepared using the following typical synthesis of AIGScores: 4 mL of 0.06 M CH₃CO₂Ag in oleylamine, 1 mL of 0.2 M InCl₃ inethanol, 1 mL of 0.95 M sulfur in oleylamine, and 0.5 mL dodecanethiolwere injected into a flask that contained 5 mL of degassed octadecene,300 mg of trioctylphosphine oxide, and 170 mg of galliumacetylacetonate. The mixture was heated to 40° C. for 5 minutes, thenthe temperature was raised to 210° C. and held for 100 minutes. Aftercooling to 180° C., 5 mL trioctylphosphine was added. The reactionmixture was transferred to a glovebox and diluted with 5 mL toluene. Thefinal AIGS product was precipitated by adding 75 mL ethanol,centrifuged, and redispersed in toluene. Sample IDs 2 and 3 were alsoprepared using this method. The optical properties of AIGS cores weremeasured and summarized in TABLE 2. AIGS core sizes and morphology werecharacterized by transmission electron microscopy (TEM).

TABLE 2 PWL FWHM Ag/(Ag + In + Ga) In/(In + Ga) Sample ID QY (%) (nm)(nm) by ICP by ICP Note 1 44 519.5 47 0.39 0.44 50 mL flask scale 2 30514 50 0.37 0.41 10x scale up of Sample ID 1 3 40 518 52 0.38 0.45 10xscale up of Sample ID 1

Example 2: AIGS Nanostructures with Ion Exchange Treatment

Sample ID 4 was prepared using the following typical ion exchangetreatment: 2 mL of a 0.3 M gallium oleate solution in octadecene and 12mL oleylamine were introduced to a flask and degassed. The mixture washeated to 270° C. A pre-mixed solution of 1 mL of a 0.95 M sulfursolution in oleylamine and 1 mL of isolated AIGS cores (15 mg/mL) wereco-injected. The reaction was stopped after 30 minutes. The finalproduct was transferred to a glovebox, washed with toluene/ethanol,centrifuged, and redispersed in toluene. Sample IDs 4-8 were alsoprepared using this method. The optical properties of the thus-producedAIGS nanostructures are summarized in TABLE 3. Ion exchange with galliumions resulted in nearly complete band-edge emission. An increase of theaverage particle size was observed by TEM.

TABLE 3 Sample PWL FWHM QY OD₄₅₀/mass ID (nm) (nm) (%) (mL · mg⁻¹ ·cm⁻¹) 4 516 38 61 — 5 517 36 58 0.87 6 520 37 53 1.04 7 514 38 64 0.72 8514 38 65 1.15

Example 3: Gallium Halide and Trioctylphosphine Ion Exchange Treatment

A room temperature ion exchange reaction with AIGS nanostructures wasconducted by the addition of a GaI₃ solution in trioctylphosphine(0.01-0.25 M) to AIGS QDs and holding at room temperature for 20 hours.This treatment led to a significant enhancement of the band-edgeemission summarized in TABLE 4, while maintaining substantially the peakwavelength (PWL).

Compositional changes before and after GaI₃ addition were monitored byinductively coupled plasma atomic emission spectroscopy (ICP-AES) andenergy-dispersive X-ray spectroscopy (EDS) as summarized in TABLE 4.Composite images of In and Ga elemental distributions before and afterGaI₃/TOP treatment showed a radial distribution of In to Ga, thusindicating that the ion exchange treatment led to a gradient of a largeramount of gallium near the surface and a lesser amount of gallium in thecenter of the nanostructures.

TABLE 4 PWL FWHM QY Band-edge Ag/(Ag + In + Ga) In/(In + Ga) Ag/(Ag +In + Ga) In/(In + Ga) ID (nm) (nm) (%) contribution bylCP by ICP by EDSby EDS 9 542 38 11 <45% 0.41 0.11 0.45 0.16 10 543 37 24 >80% 0.38 0.090.44 0.14

Example 4: AIGS Ion Exchange Treatment Using Oxygen-Free Ga Sources

Sample ID 14 and 15 was prepared using the following typical treatmentof AIGS nanoparticles using an oxygen-free Ga source: to 8 mL degassedoleylamine, 400 mg of GaCl₃ dissolved in 400 μL toluene was added,followed by 40 mg of AIGS core and then 1.7 mL of 0.95 M sulfur inoleylamine. After heating to 240° C., the reaction was held for 2 hoursand then cooled. The final product was transferred to a glovebox, washedwith toluene/ethanol, centrifuged, and dispersed in toluene. Sample IDs15 and 16 were also prepared using this method. Sample IDs 11-13 wereprepared using the method of Example 2. The optical properties oftreated AIGS materials are shown in TABLE 5.

TABLE 5 Sample PWL FWHM QY BE gallium ID (nm) (nm) (%) % source 11 52543 25 not Ga(III) deter- acetyl mined acetonate) 12 516 34 73 90 galliumoleate 13 522 35 72 87 gallium oleate 14 521 35 85 86 Ga(III) chloride15 521 35 80 89 Ga(III) chloride 16 not not not not Ga(III) deter-deter- deter- deter- iodide mined mined mined mined

As shown in TABLE 5, the quantum yield of treated AIGS nanostructurescan be improved by using Ga(III) chloride rather than Ga(III)acetylacetonate or gallium oleate when oleylamine is used as a solvent.The final materials subjected to ion exchange using Ga(III) chloridegave similar size and similar band-edge to trap emission properties asthe starting nanostructures. Therefore, the increase in quantum yield(QY) is not simply due to increasing the trap emission component. And,unexpectedly, it was found that when using Ga(III) iodide was used inplace of Ga(III) chloride, the AIGS nanostructures appeared to dissolvein the reaction mixture and ion exchange did not occur.

High-resolution TEM with energy-dispersive X-ray spectroscopy (EDS) ofSample 14 showed that the nanostructures likely comprise a slightgradient to lower In from the AIGS nanostructure centers to the surfacewhich indicates that treatment under these conditions results from aprocess in which In exchanges out of the AIGS structure and is replacedwith Ga, while Ag is present across the entire structure rather thangrowing a distinct layer of GS. This may also contribute to the improvedquantum yield of the nanostructure due to less strain.

Example 5: AIGS Core from Hot Injection of Pre-Formed Ag₂SNanostructures Mixed with Pre-Formed In—Ga Reagent

To make the Ag₂S nanostructures, under a N2 atmosphere, 0.5 g of AgI and2 mL of oleylamine are added to 20 mL vial and stirred at 58° C. untilclear a solution is obtained. In a separate 20 mL vial, 5 mL DDT and 9mL of 0.95 M sulfur in oleylamine were mixed. The DDT+S-OYA mixture isadded to AgI solution and stirred for 10 min at 58° C. The obtained Ag₂Snanoparticles were used without wash.

To make the In—Ga reagent mixture, 1.2 g Ga(acetylacetonate)₃, 0.35 gInCl₃, 2.5 mL oleylamine and 2.5 mL ODE charged to 100 mL flask. UnderN2 atm heated to 210° C. and held for 10 min. Orange color and viscousproduct obtained.

To form AIGS nanoparticles, under N2, 1.75 g of TOPO, 23 mL ofoleylamine and 25 mL ODE added to 250 mL flask. After degassing undervacuum, this solvent mixture is heated to 210° C. over 40 min. In a 40mL vial, the Ag₂S and the In—Ga reagent mixture from above are mixed at58° C. and transferred to syringe. The Ag—In—Ga mixture is then injectedto the solvent mixture at 210° C. and held 3 hr. After cooling to 180°C., 5 mL trioctylphosphine was added. The reaction mixture wastransferred to glovebox and diluted with 50 mL toluene. The finalproduct was precipitated by adding 150 mL ethanol, centrifuged, andredispersed in toluene. The AIGS nanostructures were then ion exchangedby the method described in Example 4. The optical properties of thematerial made by this method at scales up to 24× that described above,are shown in TABLE 6.

TABLE 6 Sample PWL FWHM BE QY OD₄₅₀/mass ID (nm) (nm) % (%) (mL · mg⁻¹ ·cm⁻¹) 17 510 34 96 86 — 18 524 38 93 94 1.1 19 520 38 93 88 1.3 20 51738 94 86 1.3 21 518 38 94 89 1.4 22 528 37 93 93 1.9

Example 7 Repeated Gallium Ion Exchange Improves PhotoluminescenceStability of AIGS Nanostructures 7.1 First Ion Exchange Process

Oleylamine (OYA, 2.5 L) is degassed under vacuum at 40° C. for 40 min.AIGS nanostructures (25.4 g in toluene) are added followed by GaCl₃ (127g in minimal toluene) and sulfur dissolved in OYA (0.95 M, 570 mL). Themixture is heated to 240° C. over 40 min and held 4 hours. Aftercooling, the mixture is diluted with 1 volume of toluene. Aftercentrifugation to remove some by-product, the material is washed with 2volumes ethanol, collected by centrifugation, and redissolved intoluene. After a second wash, the nanostructure is dissolved in heptanefor storage.

7.2 Second Ion Exchange Process

Oleylamine (OYA, 960 mL) is degassed under vacuum at 40° C. for 20 min.AIGS ion exchanged nanostructure, such as from Example 7.1 (12 g inheptane) is added to the OYA, follow by GaCl₃ (22.5 g in a minimalvolume of toluene), then sulfur dissolved in OYA (0.95 M, 100 mL). Themixture is heated to 240° C. over 40 min and held 3 hr. After cooling,the mixture is diluted with 1 vol toluene then washed (precipitated with1.6 vol ethanol, centrifuged) and redispersed in toluene or heptane asrequired. When performing ligand exchange for ink formulation, a furtherethanol wash is applied and the QDs are redispersed in heptane.

7.3 Alternate Second Ion Exchange Process

Oleylamine (15 mL) is degassed under vacuum at 60° C. for 20 min. GaCl₃(360 mg in a minimal volume of toluene) is added to the OYA followed byAIGS, such as from Example 7.1 (200 mg in heptane), then sulfurdissolved in OYA (0.95 M, 1.6 mL) is added. The mixture is heated to240° C. over 40 min and held 3 hr. After cooling the mixture is washedwas described in Example 7.1.

7.4 Alternate Second Ion Exchange Process

This example was carried out as described for Example 7.3, but at a 3×scale.

7.5 Alternate Second Ion Exchange Process

Oleylamine (10 mL) and oleic acid (5 mL) are degassed under vacuum at90° C. for 20 min. (Ga(NMe₃)₃)₂ (206 mg) and GaCl₃ (180 mg in a minimalvolume of toluene) are added followed by AIGS, such as from Example 7.1(200 mg in heptane). After heating to 130° C., TMS₂S (0.65 mL of 50%solution in ODE) is added over 20 min, and the mixture is held 2.5 hr.After cooling the mixture is washed was described in Example 7.1.

7.6 Results

AIGS nanostructures were subjected to an ion exchange process where Inis exchanged for Ga. The higher temperature used for this processcompared to core growth (240° C. v. 210° C.) leads to ripening so theaverage size is larger than the untreated nanostructures. Thenanostructures do not have a well differentiated shell structure. Thiscan be observed in the cross-sectional TEM elemental mapping. The lackof a higher band gap shell is expected to limit retention of thephotoluminescence of these materials during film processing.

After a second ion exchange process, the average TEM size did notincrease (FIG. 2A-2C), but the TEM elemental mapping demonstrated a moredistinct gradient to a Ga-rich (higher band gap) region had developed inthe QD.

The elemental composition for the single and multiple ion exchangeprocesses are shown in TABLE 7. Values are an average of 10-20 samplesfrom Examples 7.1 and 7.2.

TABLE 7 Sample PWL FWHM Ag/ In/ type (nm) (nm) (Ag + In + Ga) (In + Ga)Single Ion 523 34.5 0.39 0.27 Exchange treatment Double ion 523 34.10.40 0.24 Exchange Treatment

The properties of the ion exchanged AIGS nanostructures and shown inTABLE 8. Metal ratios are mole ratios determined by ICP.

TABLE 8 sample ID PWL, nm FWHM, nm BE, % QY, % Ag/(Ag + In + Ga)In/(In + Ga) Example 7.1 524.2 34.8 90 83 0.41 0.27 Example 7.2 523.634.4 90 89 0.40 0.24 Example 7.3 525.1 34.4 90 87 0.42 0.23 Example 7.4525.9 34.3 90 88 0.42 0.24 Example 7.5 524.4 33.5 90 62 0.28 0.12Example 7.6 521.0 24.5 92 89 0.41 0.18

The film PCE retained after UV cure and 180° C. bake is significantlyimproved by the second ion exchange process, as demonstrated in TABLE 9.This is believed to be due to the process of increasing the Gaconcentration in the outer layer of the nanostructures leading to agradient to a higher band gap region being introduced by ion exchange.

TABLE 9 sample Blue abs Post UV Post bake Retained ID (%) Green PCE %Green PCE % QY % Example 7.1 91.5 25.6 9.7 37.9 Example 7.2 91.9 25.816.3 63.3 Example 7.3 88.1 23.1 14.7 63.8 Example 7.4 88.5 23.7 14.962.8 Example 7.5 95.0 26.4 17.3 64.7 Example 7.6 91.0 31.4 19.7 62.8

Example 8—Compositions Comprising AIGS Nanostructures and aPolyamino-Ligand

Abbreviations

-   -   Jeffamine—Jeffamine M-1000    -   HDDA—1-6 Hexanediol Diacrylate    -   Bismethylamine—1,3 cyclohexane bismethylamine    -   PCE—Photon Conversion Efficiency

Crude AIGS QD growth solution was purified by washing with ethanol andredispersing in heptane (Solution 1). To Solution 1 was added6-mercapto-1-hexanol, heated at 50° C. for 30 minutes, washed withethanol and redispersed in heptane (Solution 2). 2 μL of6-Mercapto-1-hexanol was added per 100 mg of QD inorganic solids. Tosolution 2 was added Jeffamine and HDDA for the ligand exchanged stage,heated at 80° C. for 1 hour, precipitated with heptane, and redispersedinto HDDA (Solution 3). 83 mg of Jeffamine was added per 100 mg of QDinorganic solids. 0.42 g of HDDA was added per 100 mg of QD inorganicsolids. To an ink-jet ink composition comprising 10 wt % TiO₂ and 90 wt% of monomer was added Solution 3 and HDDA. The ink jet formulation hada composition of 10 wt % QD inorganic mass, 4 wt % TiO₂, and theremaining 86 wt % being a combination of ligands (bound and unbound),HDDA, monomer, photoinitiator, and other miscellaneous organics leftoverfrom the QD solution. This ink formulation was Solution 4.

To Solution 4 was added the polyamino ligand bismethylamine (50 mg ofbismethylamine per 100 mg of QD inorganic solids) and the compositionwas then cast as a film.

Film Casting

Solution 4 was spincoated on a 2″×2″ glass substrate. The film was curedwith a UV LED cure lamp. The film photo conversion efficiency (PCE), ameasure of brightness, was then tested. The film was then baked with ahotplate set at 180° C. for 30 minutes slightly elevated above hotplate.Alternatively, the film was baked with a hotplate set at 180° C. for 10minutes in direct contact with hot place surface.

The film PCE was then tested. A 1″×1″ masked array of blue 448 nm LEDsprovided the excitation source for the film. An integration sphere wasplaced on top of the film and connected to a fluorometer. See FIGS. 3Aand 3B. The collected spectra were analyzed to obtain the PCE.

PCE is a ratio of the number of green photons of forward emission to thenumber of blue photons generated by the test platform. While theemission spectrum from 484 nm to 700 nm is used for calculating the PCE,it is expected that the green emission has a peak wavelength between 484and 545 nm, with the major fraction of emission below 588 nm. The PCE,LRR and film morphology and reported are in TABLE 10. Unexpectedly, thepresence of the ligands 1,3-cyclohexanebis(methylamine), tris(2-aminoethyl)amine and 2,2-dimethyl-1,3-propanediamine resulted in highretention of PCE after the 180° C. bake, high LRR and no wrinklescompared to the film without the ligand.

TABLE 10 Post UV Post 180 C. Film Additive Cure PCE Bake PCE LRRMorphology No Additive 28.4% 14.1% 49.7% Wrinkles 1,3-Cyclohexane- 21.0%20.4% 96.8% No wrinkles bis(methylamine) Tris (2-aminoethyl) 12.0% 12.1%100.7% No wrinkles amine 2,2-dimethyl-1,3- 21.2% 21.1% 99.2% No wrinklespropanediamine

FIG. 1 shows the effect of diamine addition on film morphology. Thefilms in FIG. 1 from left to right contained: No additive (Wrinkling);2,2-dimethyl-1,3-propanediamine (a diamine, no wrinkling);cyclohexanemethylamine (a monoamine, wrinkling); and tris (2-aminoethyl)amine (a triamine, no wrinkling). From left to right, the first andthird films not containing the diamine exhibited extensive wrinkling. Incontrast, the second and fourth films exhibited no wrinkling.Unexpectedly, the use of a diamino ligand in the AIGS films resulted ina major reduction of film wrinkling.

Example 9—Testing of Additional Ligands for AIGS Nanostructures

In this experiment, additional ligands for AIGS nanoparticles weretested for enhanced QY, high compatibility and good thermal stability.Additionally, these ligands were evaluated for protecting AIGSnanostructures from deterioration and oxidation. Also tested were acombination of ligands that may be formulated into an AIGS inkcomposition.

Ligand exchange with these ligands were performed in organic solventssuch as ethyl acetate, PGMEA, acetone, xylene, 1,2-dichlorobenzene(ODCB), butyl acetate, and diethylene glycol monoethyl ether (DGMEE).

AIGS nanostructures were ligand exchanged with ligands that containpolymeric or oligomeric chains such as polyethylene glycol with amineand silane groups, and soft bases such as phosphino-, mercapto- andcombinations thereof for co-passivation.

FIG. 4 depicts the quantum yield values of a number of individualligands and AIGS nanostructures subjected to a single ion exchangetreatment as described herein. In this graph, NG: native AIGS; NG-NL1:amino-polyalkylene oxide about m.w. 1000; NG-NL2:(3-aminopropyl)trimethoxysilane); NG-NL3:(3-mercaptopropyl)triethoxysilane; NG-NL4: DL-α-lipoic acid; NG-NL5:3,6-dioxa-1,8-octanedithiol; NG-NL6: 6-mercapto-1-hexanol; NG-NL7:methoxypolyethylene glycol amine 500; NG-NL8: poly(ethyleneglycol)methyl ether thiol Mn 800; NG-NL9: diethyl phenylphosphonite; NG-NL10:dibenzyl N,N-diisopropylphosphoramidite; NG-NL11: di-tert-butylN,N-diisopropylphosphoramidite; NG-NL12: tris(2-carboxyethyl)phosphinehydrochloride; NG-NL13: poly(ethylene glycol) methyl ether thiol Mn2000; NG-NL14: methoxypolyethylene glycol amine 750; NG-NL15:acrylamide; and NG-NL16: Polyethylenimine).

As can be seen in FIG. 4 , treatment of AIGS nanostructures with3-mercaptopropyl)triethoxysilane (NL3), 3,6-dioxa-1,8-octanedithiol(NL5), and 6-mercapto-1-hexanol (NL6) resulted in high QY's (73.7%,72.9% and 76.1%, respectively). Thus, the invention provides AIGSnanostructure compositions comprising at least one mercapto-substitutedligand that provides improved QYs. It is believed that themercapto-substituted ligands provide high QY by passivating the surfaceof the AIGS nanostructures and reducing defect emissions.Amino-substituted ligands also improved QY.

In this single ligand test, polyethylene glycol amine-substitutedligands (L1, L7, L8 and L13), thiol-substituted ligands (L3, L5 and L6),and silane ligand (L2) showed good QY compared to native AIGSnanostructures. And, ligands L1, L7 and L8 provided better compatibilitywith monomer, when dispersed in HDDA.

FIG. 5 is a graph showing the QY % of various 2-ligand combinations thatgave improved QY % (good combination) and reduced QY % (badcombination). Surface defects can be reduced by adding a thiol ligand.The combination of L6 and L7 gave better stability than others. But forink compositions that are relatively hydrophilic, better ligands arerelatively hydrophilic ligands such as methoxypolyethylene glycol amineand poly (ethylene glycol) methyl ether thiol. This thiol also improvesthe QY by passivating surface defects.

Suitable temperatures for ligand exchange are from room temperature to120° C. The total amount of ligands in the composition can be 60% to150% of the AIGS mass.

TABLE 11 shows the relative change of QY, PWL, and FWHM before and afterligand exchange with multiple ligands. TABLE 11 shows that L6 & L7 werethe most effective ligand combinations for ink formulations, especiallywhen combined with an acrylate monomer. The combinations L2 &L7, L2 &L6, and L2 & L3, L6 and L7 provided excellent dispersibility and thermalstability. See FIG. 6 .

TABLE 11 Before After Before After Before After QY PWL FWHM LE QY LE QYPWL PWL FWHM FWHM change change change (%) (%) (nm) (nm) (nm) (nm) (%)(nm) (nm) L6, 7 55.3 61.5 531.1 531.6 36.3 36.2 +11.2 −0.1 +0.3 L6, 255.3 57.8 531.1 531.3 36.3 36.3 +4.5 −0.1 0.0 L3, 7 55.0 56.6 531.3531.1 36.2 36.1 +3.0 0.0 +0.1 L5, 7 55.0 57.6 531.3 530.8 36.2 36.1 +4.7+0.1 +0.3 L13, 7 55.0 57.5 531.3 531.2 36.2 36.1 +4.6 0.0 +0.2 L2, 855.0 57.1 531.3 531.9 36.2 36.4 +3.8 −0.1 −0.5 L3, 8 55.0 63.8 531.3530.8 36.2 36.2 +16.0 +0.1 −0.1 L5, 8 55.0 63.3 531.3 531.8 36.2 36.6+15.0 −0.1 −1.0 L2, 15 55.3 59.0 531.1 532.1 36.3 36.6 +6.6 −0.2 −0.7L3, 15 55.3 55.5 531.1 532.4 36.3 37.5 +0.4 −0.3 −3.3 L2, 13 55.3 53.6531.1 532.5 36.3 36.6 −3.1 −0.3 −0.7 L3, 13 55.3 62.2 531.1 530.0 36.338.5 +12.4 +0.2 −5.6 L2, 7 56.6 58.2 530.7 532.0 36.5 36.1 +2.8 −0.3+0.9 L2, 3 54.6 58.7 530.6 531.3 36.2 36.8 +7.5 −0.1 −1.7

Further studied were ligand combinations providing good thermalstability when heated to 180 TC for 30 min in a glove box. Ligandcombinations L6 & L7, L2 & L6, and L2 & L3 provided better stabilitythan the single ligand Li. See, FIG. 6 .

Also studied was the effect of different ratios of ligand combinationson QY. The weight ratios of ligands were varied while the total amountof ligand was fixed. The best QY was achieved with a ratio of 7:3 of L6to L7. See FIG. 7 . All combinations with L6 and L7 showed enhanced QYcompared to native AIGS nanostructures except the ratio of 9:1. Eventhough that mixture exhibited high QY, it was hard to purify asprecipitation does not occur. Mixtures of L6 & L2, L3 & L7, and L5 & L7are good ligand mixtures for AIGS nanostructures. These ligandcombinations can be used in combination with various monomers such astetrahydrofurfuryl acrylate, tri(propylene glycol) diacrylate,1,4-bis(acryloyloxy)butane, diethylene glycol ethyl ether acrylate,isobornyl acrylate, hydroxypropyl acrylate, 2-(acryloyloxy)ethylhydrogen succinate, and 1,6-hexanediol diacrylate.

Example 10—Improvement of PCE in AIGS Films

In a N₂-filled glovebox, AIGS QDs coated with appropriate ligands weremixed into inks containing one or more monomers, TiO₂ scatteringparticles and a photoinitiator. Films were cast by spin-coating theseinks, then cured using UV irradiation. The films were then baked at 180°C. for 30 minutes on a hotplate to remove any leftover volatilecomponents. All of these processes were carried out in an inertatmosphere—in a N₂-filled glovebox.

Normally at this stage, the films are measured in air by placing on ablue LED light source, with the film side facing up. An integratingsphere connected to a spectrophotometer is placed on top of the QD film(see FIGS. 3A and 3B), and the emission spectrum of the film iscaptured. The measurement is repeated with a blank glass substrate (noQDs). The blue light absorption and photon conversion efficiency (PCE)of the QD film are measured by using the following formulas:

-   -   Blue absorption=# of blue photons transmitted through QD film/#        of incident blue photons    -   PCE=# of green photons (484-588 nm) of forward emission/# of        incident blue photons

For studying the effect of air and moisture during measurement, thebaked QD films were encapsulated before they were brought out of theN₂-glovebox. This was done by applying a few drops of a UV-curabletransparent adhesive on the QD layer, then placing a glass cover slip,and curing the adhesive by UV irradiation. The QD films, thus sealedusing glass and adhesive, were measured in air using the above method.

The results show that encapsulating the QD film before measuring in airis critical to achieving a high photon conversion efficiency (PCE). TheTABLE 12 shows results from one set of films that were measured with andwithout encapsulation. For comparison, the PCE values from typical QDCCfilms containing InP QDs are also shown. When encapsulated and measured,films comprising AIGS nanostructures had higher post-bake PCE valuesthan InP, at a much lower QD loading. A further improvement in PCE wasachieved by irradiating the films by placing on a blue light source (˜6mW/cm²) for a period of 1 hour. Additionally, the QDCC films made withAIGS QDs exhibit a much narrower emission (FWHM˜30 nm) compared to filmsmade with InP QDs (FWHM 36 nm). This is a result of the lower FWHM forAIGS QDs in solution (34 nm vs 39 nm), combined with the use of mono-and poly-amino ligands that enable good dispersion in the ink resin.

TABLE 12 QD Post- Blue Post- QD loading encapsulation absorption 180° C.type in ink Encapsulation treatment in 10 μm film bake PCE PWL FWHM AIGS12.5% No encapsulation None >95% 28% 535 30 Glass None >95% 35% 535 30encapsulation Glass 1 hr irradiation >95% 38% 535 30 encapsulation withblue light InP   30% No encapsulation None   85% 32% 540 36

FIG. 8 shows the impact of encapsulation and blue light treatment over amuch wider range of samples. Unexpectedly, PCE values achieved throughencapsulation were significantly higher (greater than 32%) than withoutencapsulation.

FIG. 9 shows emission linewidth (FWHM) for films after a 180° C. bakestep and subsequent encapsulation. The median FWHM for films baked at180° C. is 30.5 nm, which narrows further upon encapsulation to 30.1 nm.This narrowing may be may be a result of the film brightening uponencapsulation.

While the samples in this study were encapsulated using glass and anadhesive, this improvement in PCE can be achieved by any method that canform an oxygen barrier on the QD layer. In mass production of devicescontaining these QDCC layers, the encapsulation is likely to be carriedout using vapor deposition processes. A typical process flow in thiscase would include inkjet printing of the QD layer, followed by curingwith UV irradiation, baking at 180° C. to remove volatiles, depositionof an organic planarization layer, then deposition of an inorganicbarrier layer. Techniques used for deposition of the inorganic layercould include atomic layer deposition (ALD), molecular layer deposition(MILD), chemical vapor deposition (CVD) (with or without plasmaenhancement), pulsed vapor deposition (PVD), sputtering, or metalevaporation. Other potential encapsulation methods include solutionprocessed or printed organic layers, UV or thermally curable adhesives,lamination using barrier films, etc.

Example 11—AIGS Inks Comprising Monomers Incorporated into the LigandsCoating the AIGS Surface

It was discovered that ligand exchange (LE) of AIGS nanostructures inthe presence of a monomer leads to higher solution QY, bettercompatibility inks and better film performance, compared to LE donepurely in a solvent. This was demonstrated through LE and filmevaluation using 16 different media.

LE of quantum dots (QDs) such as CdSe and InP may be carried out inorganic solvents to replace native ligands with desired ligands. Theresulting QDs can then be formulated into solvent-free inks bydispersing the QDs in a monomer, removing the original solvent, andadding other ink components such as scattering media and aphotoinitiator.

This procedure can be used for LE of AIGS nanostructures as well, withhigh retention of QY. However, this approach typically leads to poordispersibility of the nanostructures in monomers upon removing thesolvent. Good dispersibility of AIGS nanostructures in inks, andefficient passivation of the nanostructure surface with ligands, isnecessary to maintain film performance through harsh processingconditions such as UV irradiation, high temperature baking, etc. Thus,AIGS nanostructures that are ligand-exchanged using conventionalprocesses are not suitable for QDCC applications.

FIG. 10 shows the PLQY for AIGS nanostructures that wereligand-exchanged in various organic solvents such as acetone, PGMEA,ethyl acetate, toluene, dichloromethane (DCM), chloroform,dimethylformamide (DMF) and ethanol, at two temperatures—room temp (25°C.) and 80° C. Jeffamine M1000 was used as the ligand, with a 0.8:1 massratio with respect to the AIGS nanostructures.

Several solvents, PGMEA, ethyl acetate, toluene and DCM were veryeffective in maintaining QY after LE. Notably, LE at room temperatureled to higher QY than LE at 80° C. Other solvents tested, such asacetone, chloroform, DMF and ethanol resulted in lower QY.

However, as shown in Table 13 (o=clear dispersion; Δ=cloudy dispersion),the AIGS nanostructures that were ligand exchanged in solvents at roomtemperature had poor compatibility with HDDA, a common monomer used ininkjet printable inks. AIGS nanostructures ligand exchanged at 80° C.had better compatibility with HDDA, but lower QY. Thus, an effective LEcondition that leads to high QY and good compatibility with HDDA wasdifficult to find.

TABLE 13 Ethyl Acetone PGMEA Acetate Toluene DCM Chloroform DMF EthanolComp. ◯ Δ Δ Δ Δ Δ Δ Δ w/HDDA Comp. ◯ ◯ ◯ ◯ ◯ — — — w/HDDA (80° C. LE)

The LE study was repeated using a series of common monomers (shown inTable 14) as a medium instead of organic solvents. LE was carried out bymixing the starting AIGS nanostructures (in heptane) with a monomer,then adding Jeffamine M1000 and heating at 80° C.

TABLE 14 Monomer Name M1 Diethylene Glycol Monomethyl Ether MethacrylateM2 Ethyl acrylate M3 HDDA M4 Tetrahydrofurfuryl acrylate M5Tri(propylene glycol) diacrylate M6 1,4-Bis(acryloyloxy)butane M7Diethylene glycol ethyl ether acrylate M8 Isobornyl acrylate M9Diethylene Glycol Diacrylate M10 2-Methoxyethyl Acrylate M11Tetraethylene Glycol Diacrylate M13 Diethylene Glycol Divinyl Ether M14Butyl Acrylate M15 2-Phenoxyethyl Methacrylate M16 1,6-HexanediolDimethacrylate

FIG. 11 shows QY after LE in the presence of monomer. In all 16 cases,QY increased upon LE, and was also higher than the QYs achieved throughLE in organic solvents.

After LE, the AIGS nanostructures were isolated and purified byprecipitating in heptane, and the yield was calculated by noting thestarting and final QD mass. Unlike LE in solvents, where only a smallchange in mass is observed, the mass of QDs ligand exchanged in monomersincreased by 30-100%, depending on the monomer. Since most of themonomers tested are miscible with heptane, and would be removed upon QDprecipitation, this indicated that some amount of the monomer wasincorporated into the ligands coating the QD surface.

All 16 AIGS samples were dispersed in HDDA, then mixed into an inkcontaining scattering media and photo-initiator. Unlike thenanostructures ligand-exchanged in solvent, all 16 samples tested hereshowed good compatibility in HDDA. Three films were cast from each inkby spin-coating at 700, 800 and 900 rpm, then cured with UV irradiation.

As shown in FIG. 12 , some monomers, M2, M3, M4, M5, M6 & M8, showedhigh film EQE and can be a good LE medium for AIGS QDs.

FIG. 13 shows the blue absorption of the AIGS nanostructures film-spunat 800 RPM. M7, M10, M13, M15 and M16 provided very high blueabsorption.

Example 12 Increasing Blue Absorption with Polyamino Ligands

Typical film deposition processes includes a hard bake at very hightemperature, usually around 200° C., to fully remove any residualsolvent and volatile component. This hard bake prevents outgassingduring deposition of other layers on top of QDCC layer. This harsh bakesometimes results in very low EQE. And, either the nanostructure isdamaged by the high temperature, or the ligand detaches fromnanostructures, resulting in aggregation. Table 15 shows typical AIGSfilm EQE after UV curing and after 180° C. hard bake. Even though EQEwas good, higher than 33% after UV curing, it dropped to below 19% at180° C. for 30 minutes after a hard bake. A light retention ratio (LRR),which is the ratio of EQE after bake to EQE before bake was very low,below 60%, means that the film performance was decreased by more than40% after the bake.

TABLE 15 After UV After Bake LRR Film #1 33.7% 18.4% 54.7% Film #2 33.1%18.3% 55.3%

To overcome such a high EQE loss during the hard bake and resulting lowLRR, two approaches were tested to improve LRR.

To keep the AIGS nanostructures uniformly dispersed in entire film andprevent aggregation, diamine (1,3-bis(aminomethyl)cyclohexane) was addedto the AIGS-monomer dispersion before ink formulation. Alternatively, itcan be added to the ink formulation after mixing the other inkcomponents such as scattering media and photo-initiator in the AIGSmonomer dispersion. As seen in FIG. 14 , addition of the diamine to theAIGS-monomer dispersion before ink formulation increased EQE after UVcure and POB. EQE after UV curing was increased by 3% when the diaminewas added in an amount of 5% w/w of the AIGS inorganic mass. Moreaddition of diamine did not improve further the EQE. The effect ofdiamine on improving EQE was even higher after POB. Compared with nodiamine in monomer, EQE was improved by 5% with addition of 5% ofdiamine. With 30% of diamine addition, EQE was increased from 25% to 32%and LRR was 92%, which is similar to results seen with InP green QDfilms. The side effect of diamine was increase in viscosity as seen inFIG. 15 . However, for monomers such as ethyl acrylate, ink viscositydramatically decreased to the level of below 20 cP at room temperature.

As an alternative approach to increase EQE, better AIGS surfacepassivation with diamine was attempted. As shown in FIG. 16 , QY of AIGSnanostructures that were ligand exchanged in the presence of diamine wasenhanced by more than 12% right after LE. It should be noticed that QYof AIGS nanostructures was also enhanced after thermal treatment,simulating hard bake, at 180° C. for 30 minutes in the presence ofmonomer. The QY drop after 30 minutes at 180° C. became smaller withlarger addition of diamine for LE. At 50% w/w of diamine in LE, the QYbefore and after the thermal process were almost equal, and QY afterthermal process became higher when 70% diamine was used for LE.

The performance of QDCC films using these AIGS nanostructures wasplotted in FIG. 17 . Film EQE was better when the diamine was used forLE compared no diamine in LE, and the enhancement was even higher withmore diamine addition up to 50%. EQE obtained with 70% diamine additionand LE was lower than 30% and 50%. It is suspected that when higheramounts of diamine is used for LE, the amount of diamine incorporated onthe AIGS surface increases, but this decreases the amount of ligandsand/or monomers on AIGS surface. The observed decrease in QD mass afterLE with diamine is likely the result of fewer ligands and/or monomer onQD surface. This occurs as well when the diamine is added to the monomerfor LE, which results in increased ink viscosity.

When these 2 approaches are used to improve film EQE, as seen in FIG. 19, the effect of diamine on film EQE was highest when diamine was addedin both the ligand exchange and monomer dispersion. The viscosity doesnot necessarily depend on the total diamine amounts in ink. The highestdiamine amount sample, where diamine was used in both LE and monomerdispersion, had a middle viscosity. This viscosity was lower than whenthe same amount of diamine was used only in LE.

EQE enhancement using diamine in LE and/or monomer dispersion was testedwith 1,3-bis(aminomethyl)cyclohexane, and an additional 5 otheradditives listed in Table 16. All additives had similar effect oninitial EQE and A1, A5 and A6 were slightly better than others whendirectly added with the monomer. However after hard bake, A1 and A6 werethe 2 best additives in final film EQE. In addition, good EQE wasobtained without using the same additive in LE and monomer additionamong the listed amines. Even when the same diamine is used in LE andmonomer addition, its effects in improving EQE can be different. Forexample, as seen in FIG. 23 , A6 was effective for retaining EQE as wasA1 when used in the monomer addition, however it was not as effective aswhen A1 was used in LE.

TABLE 16 additive list A1 1,3-Bis(aminomethyl)cyclohexane A21,7-Diaminoheptane A3 Cycloheptylamine A44,4′-Methylenebis(2-methylcyclohexylamine) A5 Cyclopentylamine A62-Methyl-1,5-diaminopentane A7 4-Aminopiperidine

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. It will be apparent to persons skilled in the relevant artthat various changes in form and detail can be made therein withoutdeparting from the spirit and scope of the invention. Thus, the breadthand scope should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

All publications, patents and patent applications mentioned in thisspecification are indicative of the level of skill of those skilled inthe art to which this invention pertains, and are herein incorporated byreference to the same extent as if each individual publication, patentor patent application was specifically and individually indicated to beincorporated by reference.

1-30. (canceled)
 31. A method of preparing a film comprising Ag, In, Ga,and S (AIGS) nanostructures, comprising: admixing at least one organicresin with AIGS nanostructures and at least one ligand to form anadmixture; preparing a first film comprising the admixture on a firstbarrier layer; curing the film by UV irradiation and/or baking; andencapsulating the first film between the first barrier layer and asecond barrier layer; and wherein the encapsulated film exhibits aphoton conversion efficiency (PCE) of greater than 32% at a peakemission wavelength of about 480-545 nm, when excited using a blue lightsource with a wavelength of about 450 nm.
 32. The method of claim 31,further comprising: addition of at least one oxygen reactive material tothe admixture, forming a second film comprising at least one oxygenreactive material on top of the first film; or forming a sacrificialbarrier layer on the first film that temporarily blocks oxygen and/orwater; measuring the PCE of the film, then removing the sacrificialbarrier layer.
 33. The method of claim 31, wherein the method isconfigured to yield a film comprising AIGS nanostructures having anemission spectrum with a FWHM of less than 40 nm.
 34. The method ofclaim 31, wherein the method is configured to yield a film comprisingAIGS nanostructures having an emission spectrum with a FWHM of 24-38 nm.35. The method of claim 31, wherein the method is configured to yield afilm comprising AIGS nanostructures having a quantum yield (QY) of80-99.9%.
 36. The method of claim 35, wherein the method is configuredto yield a film comprising AIGS nanostructures having a QY of 85-95%.37. The method of claim 31, wherein the method is configured to yield afilm comprising AIGS nanostructures having an OD₄₅₀/mass greater than orequal to 0.8 mL·mg⁻¹·cm⁻¹, where OD₄₅₀ is the optical density of thefilm when irradiated with electromagnetic energy having of wavelength of450 nm.
 38. The method of claim 37, wherein the method is configured toyield a film comprising AIGS nanostructures have an OD₄₅₀/mass in theinclusive range 0.8-2.5 mL·mg⁻¹·cm⁻¹.
 39. The method of claim 31,wherein the method is configured to yield a film comprising AIGSnanostructures have an average diameter of about 5 nm.
 40. The method ofclaim 31, wherein the method is configured to yield a film comprisingAIGS nanostructures such that at least about 80% of the emission isband-edge emission.
 41. The method of claim 40, wherein the method isconfigured to yield a film comprising AIGS nanostructures such that92-98% of the emission is band-edge emission.
 42. The method of claim31, wherein the admixing at least one ligand comprises admixing apolyamino ligand.
 43. The method of claim 42, wherein the admixing apolyamino ligand comprises admixing a polyamino alkane, apolyamino-cycloalkane, a polyamino heterocyclic compound, a polyaminofunctionalized silicone, or a polyamino substituted ethylene glycol. 44.The method of claim 42, wherein the admixing a polyamino ligandcomprises admixing a C₂₋₂₀ alkane or C₂₋₂₀ cycloalkane substituted bytwo or three amino groups and optionally containing one or two aminogroups in place of a carbon group.
 45. The method of claim 44, whereinthe admixing a polyamino ligand comprises admixing1,3-cyclohexanebis(methylamine), 2,2-dimethyl-1,3-propanediamine,tris(2-aminoethyl)amine, or 2-methyl-1,5-diaminopentane.
 46. The methodof claim 31, wherein the admixing at least one ligand comprises admixinga compound of Formula I:

wherein: x is 1 to 100; y is 0 to 100; and R₂ is C₁₋₂₀ alkyl.
 47. Themethod of claim 46, wherein x=19, y=3, and R² 32 —CH₃.
 48. The method ofclaim 31, wherein the admixing a polyamino ligand comprises admixing(3-aminopropyl)trimethoxysilane); (3-mercaptopropyl)triethoxysilane;DL-α-lipoic acid; 3,6-dioxa-1,8-octanedithiol; 6-mercapto-1-hexanol;methoxypolyethylene glycol amine; poly(ethyleneglycol) methyl etherthiol; diethyl phenylphosphonite; dibenzylN,N-diisopropylphosphoramidite; di-tert-butylN,N-diisopropylphosphoramidite; tris(2-carboxyethyl)phosphinehydrochloride; poly(ethylene glycol) methyl ether thiol;methoxypolyethylene glycol amine; acrylamide; or polyethylenimine. 49.The method of claim 31, wherein the admixing a polyamino ligandcomprises admixing a combination of amino-polyalkylene oxide andmethoxypolyethylene glycol amine; amino-polyalkylene oxide and6-mercapto-1-hexanol; amino-polyalkylene oxide and(3-mercaptopropyl)triethoxysilane; or 6-mercapto-1-hexanol andmethoxypolyethylene glycol amine.
 50. The method of claim 31, whereinthe method is configured to yield a film that is 5-15 μm thick.